your in high school so it isn't unreasonable that her public image is what rules most of her decisions. In the real world people don't really care if your gay/bi or not (and i can guarantee that most guys would find it hot), but in high school, its silly but no kid wants to be the freak, and i guess that's what she is afraid of.
I think you might have to talk to her more about your feelings and hers to see if there is any potential between you two ( it doesn't sound like she is gay/bi, but I'm not there). But either way, stay true to yourself and how you feel, other people only affect you as much as you let them. And high school is a VERY SMALL portion of your life, so don't be afraid to be you.