I see three things here:
- Ann has a history of repeatedly pushing you.
- You've had only 1 good conversation about XYZ so far.
- That conversation had some points that made you change your mind, and you're now thinking of doing XYZ.
My parents can be pushy. They'll repeatedly tell me to do things, or change the way I do things. But it often takes a conversation like the last one you had with Ann to change my mind: I don't need to be told to do things a certain way over and over, I need to be explained why doing things a certain way is better, I need to hear their arguments, not just their opinion. And, like Ann, years ago my parents saw me changing my mind as their personal victory, as a result of their repeated reminders, and not as a conscious choice from my side that was made based on mutual understanding.
For me, it has helped to voice this to my parents, and keep it separate from doing XYZ. So my advice to you would be to first have a good conversation with Ann, that focuses on how much better you liked having the conversation where she did listen to your concerns, and provided counterarguments. Tell her that for you, there's such a clear difference between her behaviour before (texting, bringing it up at every occasion) and the good conversation you had. Point out specifics. Basically, tell her everything you told us here, and perhaps more.
But keep XYZ out of that conversation. Don't immediately tell Ann that you're now thinking of doing XYZ. If you can, don't do XYZ before having had that conversation, and don't do it immediately after either. That way, Ann will hopefully have time to process what you had to say about the conversation without associating it with XYZ.
Eventually, you do need to tell her that the good kind of conversation helped you change your mind on XYZ, while all other the other things she did never helped. This may just be a casual line at the end of the conversation, but make sure to only tell her about doing XYZ once you have the firm impression that she gets the part about communicating. If that point doesn't come, don't tell her about doing XYZ. You might even refrain from telling her until she's trying to get you to do ABC by preaching again, by telling her at that point it wasn't her preaching that made you decide to do XYZ.
You're probably going to need to have multiple conversations about this. You should be ready to repeatedly remind Ann about how you like to talk about these things when she's on to having you do ABC. You need to keep complimenting her or expressing your gratitude after having had a good kind of conversation. In the same way, you need to tell her when you're not up to having one or remind her of the good way to talk about things if she's just preaching again.
For me, I had to have a few similar conversations with my parents, most of them made without relating it to any specific thing they wanted me to do or which I had in the past changed my mind on. It worked, to an extent. They will still point out things to me, and they will still ask me to do so repeatedly. But we're now at a point where, if things are brought up a few times, we'll end up having a conversation where we will exchange arguments and viewpoints, and sometimes I end up changing my mind, sometimes they see I have a point and will stop asking. And we all understand now that repeatedly bringing something up is not the thing that changed any minds, that it was only the thing that sparked the meaningful conversation.