A while back I told my aunt I was gay and I dismissed it and said it was just a phase. Then I told her I was bisexual, and she is supportive of LGBT, and told me to give it time and to go with the flow. Well, I have finally figured it out and I am transgender. How am I gonna tell her I'm a girl trapped in a boy's body and that I plan on getting a total sex change operation when I am older(like after college)? Thanks!!!
I am no expert, but you could try just telling her. If you live far away, call her up and tell her it's all about that. If she lives close, go over and do something similar. If you see her regularly, you could just tell her outright (she seems OK with it from that reaction), or kind of hint at it so she initiates the conversation. This latter option is fairly effective for me. I told my mom like that - I just asked about LGBT issues for a while, then asked "what would my name be if I were a girl?". She started the conversation and, for me at least, that made the awkwardness her fault. Or something You say that she is pro-LGBT. So you have nothing to fear. What is the worst that could happen? If she abandons you, how much does it matter? And conversely, why do you need to tell her? Does it matter if she knows now? The chances are that at this stage, the answers to these questions should tell you if you should tell her or not, and if you are ready. If the effects of telling her and it being the worst case are better than not telling her at all, just ring her. If it is a closer balance, buy her some dinner, or be subtle. I hope I helped on some level.
If she's supportive of LGBT people, and she says it that way herself, you should be fine, because LGBT includes transgender, that's what the T stands for. Hope this helps