My mom is going to have a hard time with it too. She has already told me that I can't be genderqueer because I am het "daughter." Due to her mental health history of delusions and paranoia, I worry a lot about how she will respond to my transition (specifically the risk that she might develop a Capgras type delusion in which she is unable to believe that I am her child, instead believing that something horrible has happened to me and I was replaced by a stand-in).
Definitely don't want to put her through that on my account. But I know I'll probably have to, and soon, since I'm working at her old psychiatric facility and I'm out at work...
It really sucks that our families have to suffer for us to become happy - but at the same time, we cannot keep suffering just to try to make them happy.
A mother's love is supposed to be a force that can conquer anything, so if you have that, and she is scared for you, or worried about you, or just hurting because she knows you have been hurting, then she will probably get through it okay. For those who did not have that unconquerable mother's love, transition can be even more lonely and painful. So hold on to whatever feelings your mother has for you, even if they are painful, because it means an opportunity to strengthen your relationship at the very time when for some, that relationship can be completely severed.
Sorry if I got too bright-sidey. I'm trying to convince myself, to a degree, if I'm being honest.