It's impossible to know, of course, until you ask her, but I see other possibilities as well:

— She is illustrating a healthy parent/child relationship/bond (I think you said you are a mother as well?).

— She does it for herself, to put some space between your growing need and her need for autonomy (the same way a woman might talk about her boyfriend a lot to a male co-worker).

— She forgets that it's upsetting to you.

Anyway, it's hard to know, but from everything that you've written about her, she has fostered a close relationship with not much protection for you emotionally. You've benefited from it, but at the same time are now feeling the pain of it.

This is why therapists have to be careful and really know what they're doing. I'm not saying yours doesn't, but this is definitely something that's weighing on you and needs to be worked out so that you feel stronger between sessions.

You have what sounds like good, open communication. I hope you work it out soon.