her behavior is WRONG. nothing to do with her being a lesbian or not. the problems are
1. you are 15 she is an adult
2. she is your teacher you are her student
3. it should be obvious to her that her behavior is unwanted yet she persists

i'm bisexual so trust me, my opinion has nothing to do with homophobia. i was briefly a high school teacher, and i would never treat any of my students this way and would immediately report any teacher doing this to a student, regardless of what the gender was. this is sexual harassment bordering on child molestation.

report her to as many authorities as possible - principal, school board, police - to make sure that action is taken and it's not just swept under the rug. she needs a criminal record so that she can never teach children/teens again or have any job working with them.

if you don't report her, she will do this to other students and will probably take it even further if she can, waaaay further. she's a sexual predator.