I think it's awesome you did that research. I think you could open it up by saying something like 'I've thought a lot about our conversation. I did some reading this week and I think that I might be an extrovert, blah blah.'

I would be careful about labeling her an introvert. It would be better, imo, to talk about your own feelings in this matter and how your research relates to the way you behave. Let her volunteer that she is an introvert, don't tell her that you think she is one. Asking if she prefers alone time to recharge is okay, but sometimes it's irritating to be labeled. It can feel accusatory even when it isn't (I find).

I hope you guys can work it out - you have a very thoughtful approach!