May I suggest you think carefully Josh. Is she defensive still about her situation?
I say this because, a few years ago, I met someone who was transisioning. I sat down at a table, occupied by a group of girls, one of whom I knew. I didn't notice anything, until one of them pointed out that another was transgender.
I tried very hard to discuss, but was rebuffed. She was clearly very defensive and probably feared my interest might be voyueristic.
One the other hand, if you think your cousin will take it well, then she could be a good ally