Danielle,
You are not silly to feel as you do. It hasn't been long that you have realized you are trans. I am not trying to quicken your pace of coming out if you are not mentally ready. I guess I would like to let you know that all these things that you see as, "OMG, I can't do that. People will turn their back on me." All the collective fears, are possible to get past and have a good quality of life without the trans monkey on your back. It was 3 years ago that I went to the Philly Trans conference that Claire spoke of. I was dressed as I guy except I had a bra under my male clothes and a bracelet on. I was really really scared. The fear that someone might think of me as something other than that safe outer shell I had used for so long, was paralyzing. Well, taking things a step at a time, today I am 97% transitioned, female and loving it. Oh, and I had two grown sons to get on board with all my changes. You have to decide your pace. I guess I am writing because these fears can make you put your happiness on hold for a long time. If you are sure that transitioning is right for you, putting it off will not make doing it any easier.
After hearing about your sister, I wonder if the treatment she got had a lot to do with her personality. You being a very different person, could see very different treatment. As you come out, the fear doesn't stay forever. Well, in my case anyway. I shouldn't speak for everyone. My fear turned into a sense that others have no right to judge me or treat me badly because I am trans. At some point you can develop pride in being how/who you are too. Unfortunately, you really can't skip the hard parts to get there. Just know that you can do this.
Moni