Terrified

That could work if you think she'd read it. If you don't want to talk to her in person a letter is a good idea. You should definitely point her towards some sort of resource, whether it's the book or a website or anything else you think of. In the end, it's your choice and you should do whatever feels right. If you decide you're not ready to come out, that's ok too.

 

Don't come out to her unless its safe to. Please. If you feel like you have to, at least test the waters first. Try to drop political questions to gauge her opinion on the LGBT community and trans kids specifically. You said she's mentally abusive with anger issues. This describes my mom and i don't plan to tell her until i'm moved out, not dependent on her, and can easily cut her out of my life when she inevitably blows up and throws every insult at me in the book and brings up her whole childhood and mine and bans me from ever coming around the house and then proceeds to tell everyone. I know she will.

 

I would have to agree with Lunarlyric on this one. Do not come out rashly. Rationalize your feelings and test the waters first. My mother have always expressed in actions and words that she doesn't like gays and doesn't want I and my brother to be gay. I didn't tell my mother, he just found out herself by snooping into my wallet and phone. We had an argument about privacy and not talking about her about myself. But I do not want to take the risk. Save yourself first. This is not selfish and you are not required to disclose anything to anyone until you are ready - emotionally, physically and financially. You know your mother but do not underestimate her capacity to understand and accept you. Leave some doubts but take the safer path as of this time.