I finally broke down and told my sister. Her and I have kind of a weird relationship, as in we usually dont get along when we are in the same household, but we're like best of friends when physically separated. The fear that I had was that if I told her, she'd tell my parents, and life = ruined - my parents could do some terrible things to my life, even with me having my own apartment and being only 4 months from graduation from college.
But, after finally having her agree that she wont tell my parents, I spilled the beans to her. Life story. At first, she didn't understand ->-bleeped-<- or GID, not really knowing anything about it, even with many of her friends being gay. So I explained what it was, told her about how I've felt all my life, and told her what ive done and where I am now (and how things are changing in the future).
I did it over IM because I broke down several times during it all, and it wouldnt have been good for her to see that - one of her friends died last week in a car accident, and I dont want her to see any more sad people right now.
She still doesn't totally understand the transgender part (not an age issue - she is 20), but then I told her about the effects of the emotional pain, she understood. She also can see things differently than my parents can see things, about how if they aren't in control, they lash out and get verbally abusive, among other things.
All in all, I think she is supportive of it. I say think as, she supports me as flesh and blood, and she knows that this is something that I have to go through, and she doesn't want to see me in pain. But think as in I don't think she doesn't totally see it as religiously acceptable. Still, overall, I think she is supportive, which is something I wasn't totally expecting.
She is going to spend a few hours thinking it over - she had a shopping date with friends so that'll give her time, and we're gonna talk later tonight.