I know how you feel!
My Mom is, in some ways, my source of greatest emotional support but can be the most painful thorn in my side. She's a VERY negative person. She's retired, stays home most of the time and has no friends; Her world is very small.
I've been out to her for almost 3 years; It's like I have absolutely no credibility with her... Even now we'll be talking and I'll feel like she's patronizing me. Sometimes I feel as if she doesn't believe me when I talk about the pain I felt when I was young. I think that it may just be a "parent" thing from her generation, the time when children were best seen but not heard. No amount of documentation that I've provided has changed my mother's mind about Transsexuality.
The fact that she's going to the appointment, however, is a good sign. I wouldn't focus on trying to get her to validate your Transsexuality. No one, regardless of how many letters follow their name, is going to change her mind about the issue. You've already provided an accurate description of GID.. Someone else trying to convince her that it's real might be a waste of time. I would concentrate on what your therapist can help her identify as what will be helpful to you. Examine the dynamics of your relationship. It might also be helpful to validate HER feelings about what's going on... Parents that have a Trans child sometimes feel as if they failed in some way... like there's something different that they could have done that would have prevented our condition. It's a transition, of sorts, for her too.
If it helps, I can tell you that things with your Mom might improve over time. You can't count when you came out as the first time she had to deal 100% with your being Trans. It's when they SEE it, the physical changes, that they realize that it's not just talk or a phase. This Christmas, my Mom gave me a card addressed to "My Special Daughter." I cried when I read it because that was the first time she really acknowledged it... It might happen, it time, for you.... just give it time. :-)
