Why does she keep acting this way around me?

[Jaime]

So there's this girl who i added on Facebook like 2 years ago. She seems really really nice and friendly. I've met her through my friend and sister a while back which she was really nice but she probably doesn't remember. So i added her on Facebook and she would like my statuses. I guess she thought i was my sister since we look a bit similar. I commented on her photo and said she was pretty and she said thank you. I told my friend who knows her that i thought she was pretty and cute (i had a bit of a crush on her) which my friend i guess asked her if she knew me and she said no.

So i guess weeks later, she deletes me on Facebook. I see her at school and she would give me weird looks and sometimes like she wants to kill me. Every time i would see her, she would just give me a look. Whenever i am close by her, she would get move away from the area. I saw her hanging with my group of friends and i was walking to them and she saw me walking towards that area and she said "Got to go k? bye" and hugged one of my friends and left as i came. She STILL does that now after 2 years which it is actually annoying me since i don't know what i did wrong. I have a boyfriend which we've been dating for 7 months now and we hold hands so she should know that i don't have a crush on her or an obsession..she STILL gives me looks and keeps distant from me. Now whenever she is around, i distant myself from her because i can't stand people giving me looks nor do i like making people uncomfortable..
We're both bisexual. She has a girlfriend. She still stares and I try not looking but she just does