It's lucky you have someone so close to you who is trans. You are both stunning, but I feel like I'm preaching to the chior. Your uncle seems like a very logical man, and you are very lucky to have him too, he obviously sees his girlfriend as a woman, and nothing else. Sorry, that was off topic, but now to the point. It might help to print off the WPATH Standards of Care (
http://www.wpath.org/documents2/socv6.pdf), and give them to your therapist, and also to direct her to the WPATH website (
http://www.wpath.org/). The WPATH, or the World Professional Association for Transgender Health was formerly the Harry Benjamin International Gender Dysphoria Association, or HBIGDA.
Good luck Jocelyn, and I hope that the letter acquisition goes smoothly!