Although it's fair for you to ask for alone time, the way you ask it is important too, to prevent from coming across as wanting to avoid her.
Source: Am Belgian, live in Belgium with my New Zealand girlfriend. In 4 weeks, we'll be heading to Australia/NZ for 5 weeks to visit her family and see the sights.
I suggest you don't ask her to not join you (because that makes it come across as not wanting her there), and instead elaborate on where your priorities lie if she were to be present. Something like:
I haven't seen my family and friends for a long time, and I only have limited time to spend with them. I want to make the most of it, and I'm afraid that you'll feel like I'm ignoring you.
I picked this phrasing for a few reasons:
- You're not communicating that you've already decided that she shouldn't come; which can make her feel excluded.
- You're not telling her to not come, but you are addressing the fact that she won't be your main focus during that time.
- You're including your main justification, which is pretty much unrefutable: a limited time window to see family that you haven't seen for three years.
A bit more detail
That's a basic approach that, according to me, explains the problem while avoiding making her feel shut out (both by making the decision for her, and excluding her from meeting your family).
However, based on your relationship status and future plans, there are a few differences here.
If the relationship lasts; will you stay in France? Has this been discussed?
Me and my girlfriend talked about this, and even though we currently live in Belgium, it's likely that we will return to Australia/NZ in a couple of years.
If you already agreed to stay in France, or it hasn't been discussed yet, then your girlfriend's suggestion to meet up makes a bit more sense:
- She may consider it a rare opportunity to see you in your "natural" environment (I'm similarly interested in seeing my girlfriend in a location she's familiar with)
- She may not have considered the emotional impact living abroad has had on you. She has her family closeby in France and may simply have lost track of the fact that you're there without family. If you never really complain about missing your family (because you're taking responsibility for your own decision to live abroad, or simply aren't one who easily complains), then she may not even have considered that you miss your family.
Phrasing. Phrasing. Phrasing.
I do not want to "deal with her" while I'm there; she tends to be very attached and I don't know how much time I will have for her.
Although I am fully onboard with your justification, and the fact that asking for time with your family is more than fair, I can't see a way for this (quoted) statement to not blow up in your face. It lacks interpersonal skills and leaves much to be inferred about how you consider her a burden.
- Don't use the phrase "deal with". Most commonly, you deal with problems, and you're implying that she's a problem.
- Don't call her "very attached". In the current context, it's equivalent to "too attached", which is essentially berating her for how she's approaching the relationship. Note: if she does actually have overattachment issues, you can address that at another time. Don't do it during a conversation where you're telling her you don't want her near you.
Stick to the facts. Tell her things that are undeniably true and do not imply negative things about her.
- You miss your family.
- You have a short time to be with them.
- She might not like it if she's with you while you're mainly focusing on your family.
Stick to those facts, and let her fill in the blanks. Maybe she decides that she doesn't want to feel ignored and will prefer to keep travelling instead. Maybe she really wants to see you interact with your family and is completely onboard that she's not going to be your center of attention.
A few things to avoid
These are tangential comments, mostly subjective. You can disagree with these, but I thought they would be relevant footnotes:
- Don't make the decision without involving her. It's presumptuous. Be inclusive of her, since you're supposed to be partners. Instead of telling her how it's going to be, raise a problem and include her in finding a solution. If she's unsure how to solve it, you can still offer your "decision" as a suggestion, and you will have already avoided putting an ultimatum before her.
- Don't be convinced that she shouldn't really be there with you. Again, you're partners, and part of that is sharing your lives. The problem you have isn't related to her presence, so don't solve it by making her not be present. The problem lies with where dedicate your attention during those three weeks. So make that clear to her, and allow her to be present if she's not claiming your attention. That way, you can likely both get what you want without anyone being left out.
- As your partner, she should be able to recognize when something is important to you, even if that conflicts with what she wants. Working under that assumption (since you are in a relationship with her), your main focus is to get her to understand why being with your family during those three weeks is important to you.