I am going to give an answer even though the OP is long gone from the site and it is probable that they are never going to read it. Other answers have covered concerns about authority and the appropriateness of commenting about attire in the presence or absence of a formal dress code. For this answer I am going to assume there is neither a position of authority nor a formal dress code, so it basically boils down to:
- how and to what degree you can be supportive
- where sensitivities and pitfalls may be
As a transwoman in my fifties I'll start with the latter and share some of my personal experience and borrow from others I know. They're a varied lot and each has different coping mechanisms for dealing with the stresses involved in transitioning, some carried over from the past, some fairly recent. You will have to figure out which apply in this situation regarding dress style and clothing. Work with them as you are not their therapist.
Transitioning at fifty
This means that you passed as a male for the formative years of your life, childhood to late adolescence. Whether that decision was yours, conscious or not, or foisted upon you by your social environment does not matter. It does however mean that you have not had the benefit of decades of feedback from your female elders (mother, aunties) and peers (girlfriends, sisters) on female mannerisms and clothing styles to find your own style or set of styles, fitting the social setting. Transitioning you will have to cram all those decades into a few years at an age where learning is slower and often without the benefit of BFFs for feedback. I cope by observing and copying and slowly develop my own style which may not be entirely age appropriate (I copy from live females that I find attractive which are usually younger than me) and is a bit garish on the accessories. Others pick a look from magazines, say 'vintage', and go for that.
The limitations of our bodies
Hormone replacement therapy changes our bodies slowly but steadily in a few years, among which more fatty tissue, less muscle. Some things that nature (testosterone) has done cannot be undone, not even by surgery, such as the skeleton. We will always have broader shoulders, bigger feet, a wider chest and fairly slender hips for a given BMI compared to cisfemales. Unfortunately, this means that mass produced female clothing and shoes don't fit us very well. Some of us accept that we cannot have everything and pick clothing to work within the parameters of our bodies, such as wearing tops and bottoms in different sizes. Some of us have a hard time accepting that and cram themselves into fits that are off. Or we go to a specialty store.
Money may be a concern
It takes a good deal of money and several years to fill up a wardrobe of female clothing, including shoes and accessories. Unless you are loaded and many transwomen aren't, you'll have to buy on a budget, because transitioning, even if covered by insurance, has all sorts of associated costs. If you have to go to specialty stores or tailor-made then it becomes even more expensive. Maintaining sets appropriate for different environments (work, leisure, party) also adds to the cost. Due to our changing bodies (HRT) we may need to renew substantial parts several times over. Three pants and a skirt I wore comfortably 6 months ago do not fit me any more by a long shot and, with any luck, I am looking forward to the day that I have to replace all my bras. Early, while developing your style, you buy the wrong things. I have two skirts which I am unlikely to wear outside ever because, well, they're really too short. I cope by buying cheap in sales and second-hand, except for underwear. Others, if they have a background of cross-dressing before transitioning, use those outfits, which unfortunately tend to cater to fetish environments - as do some of the specialty stores -, as a base for their wardrobes.
Transitioning is liberation
After having spent decades trapped in a body that you are uncomfortable with and expressing a gender that you aren't, it feels incredibly liberating to become more female every day and to be able to express your femininity day in day out. Nobody but yourself is ever going to take that away from you. Most transwomen plan this out quite consciously. I gradually changed my appearance over the course of six months, going full time female two months before HRT started. Others do the big bang thing, changing expression overnight. Still others wait with changing their public appearance until HRT and facial hair removal is well underway. And there are also those that favor an androgynic appearance so nothing much changes in the way of gender expression. For those that value their female gender expression greatly, they may lack confidence and experience. Critique can come across as an attempt to take this new found liberty away, so tread carefully there.
Psychological effects of HRT
HRT also messes with our brains especially with our aggression and response to (perceived) aggression. Early in HRT we go through a kind of reverse menopause (in months, not years) as our brain adapts to estrogen. The effect is highly individual and dependent on the method of administration, for some nothing much changes, for others it is profound and includes a monthly mood cycle. And sadly, some of us do get depressed (common side effect of some anti-androgens and progestins). For me the effect is not so great, I am less competitive, more communicative and feel more mellow for want of a better word. Nevertheless, I found that I do have to change some of my coping strategies in stressful situations especially where I am confronted with (perceived) aggression. Still working on that, I suppose. Others I know have similar issues with coping strategies they had as a male but seem no longer relevant. Sexual orientation (romantic and .. uh .. whatever rocks your boat) may change but there is a lot of variation there, much more so than in the general population. That said some of us do dress to attract the attention of the desired gender and some of us do go over the top. This is a part of self-discovery, how to fit your sexuality in your new gender expression.
What to do?
Unless you plan on alienating her (this is unfortunately not all that uncommon), the only means to achieve your objective, getting her to dress more appropriately, is to be supportive and through that support expand her view on female gender expression so that she chooses herself to dress more appropriately in the office environment in a style that is her own.
To what degree you want to be supportive is your own choice. I'll lay down three scenario's and you can take your pick from those.
We're only coworkers and I'd like to keep my distance
Fair enough. Here is what you can do, offer constructive criticism or feedback. This is more effective way of giving her the benefit of decades of experience. The pattern is somewhat like this:
- wait until she is ready to receive feedback (idle, somewhat safe, no eavesdroppers)
- ask before you give. If the answer is no, then leave it.
- start with something positive, do not go to the next item with a 'but', 'however' or something like that (it is implied, not said)
- state one or more negative aspects. Be specific and let it be about observable things, do not judge. If there is a judgement call, couch it with "I feel that .." or "I think that .."
- state how the negative aspect affects you and others
- suggest viable alternatives
To give an example:
Hey, can I say something about your outfit?
I like the contrast between your top and bottom and your nail polish gives it a nice touch of color
Given the length of your legs, I feel the hem of your skirt should be considerably lower than three inches below your crotch.
The way it is now, when you sit down and it rides up just a little or like when you cross your legs sitting down, anyone can see the color of your panties. It is okay for parties when you are standing all the time, I guess.
You can avoid that by keeping your knees and thighs tightly together all the time or by wearing a longer skirt. Just over knee or under knee will do fine.
Be prepared to receive and possibly invite feedback on your style of clothing. Don't become defensive but do give explanations about the choice's you have made.
You always wear ankle skirts!
Sure, I frequently like to spread my knee a few inches apart when sitting down. Wearing an ankle skirt I do not have to worry about someone accidentally looking up my skirt when I do.
Use this method occasionally, nothing can be more aggravating than a colleague that is forever on your case.
I don't mind a bit of personal involvement
Fun. This is where you get to share.
First, you have to gain her trust. You do this by sharing some of your experiences from childhood, puberty and early adolescence regarding clothing and the effect it seems to have on others, including the mistakes you have made and emotional content. Reminiscing is a nice format. You can do this more often but do it in a safe place without eavesdroppers.
You know, when I was a kid, I liked to climb trees a lot. But as things go, there was a bunch of boys that looked up and called me out on seeing my panties. I was so embarrassed! I hated every minute of it. You know what my Mom said when I complained to her about it? 'Boys will do that when they're a certain age. Either you stop climbing trees or you wear pants or shorts when climbing trees', So I gave up on the trees, but I did regret that on more than one occasion.
Once she opens up you can ask her things, like where she gets her clothes from. This is as much give as take, you also get to tell where you buy your clothes. And complain about stores whose clothing never fits properly because you are not shaped like a supermodel.
Finally, with sufficient rapport you can take constructive criticism (see the first section) a level deeper because you can now also talk about the unwritten rules or your interpretation of them.
I want to do more!
Most women like a bunch of female friends to hang out with, discuss life issues and go shopping with. Transwomen are no different.
So, become a friend. If you are already personally involved (see the previous section) then this is just the next level. Hang out and have tea somewhere out of the office environment. Invite her to go shopping together (for clothes) and while shopping show her how she would look just as feminine in more appropriate clothes without coaxing her into something she does not want and is probably not going to wear.
Once you are friends and get to know each other quite well, you can bring up the subject of appropriate clothing one more time. You can state your opinion and she can state hers and that's that, you can both respect each other's opinion. I am not sure at this point whether it will really matter to you what she is wearing.
