Is it normal to feel this way about my sister?

Incest is horribly tabooed in our society. Sure, it can cause genetic problems, but as long as one is being smart and safe, it isn't a problem. Having safe sex with another is perfectly healthy and fine. Especially if you two are the same sex, which eliminates the pregnancy issue. related by blood or not, people are people, and they can get attracted to each other. I think you shouldn't suppress these feelings, but if she doesn't share them then don't push them. Don't force her to do anything.