Advice needed!

Hi, I'm Jess and I'm 17 and diagnosed with Asperger's at 14. Recently, school has been really hard. I thought I had found a nice group of friends to hang about with at break times and lunch times, and was happy. But recently I found out that they are always talking about me, and leaving me out. There is this one specific girl that has been worse. When I first found out I had Asperger's, I told her and explained how I felt in order to see if she could maybe change the way she treated me. I now feel like she uses that information and toys around with me to make me feel bad eg. not inviting me places,running off to lunch without me, not sitting with me. I have spoken to her a lot about this over the couple of years, saying that I don't think it's fair. She never listens to me and I always end up very upset and having a  meltdown. No one really knows how bad she makes me feel, but I have no one else due to her not wanting me to talk to the people she doesn't like, or she would go in a mood with me. I literally have no one else at school and although it is nearly summer, I know it will ruin my summer knowing that I am hated. I would literally have moved the earth for her. She can make me feel so special and the next, awful. I honestly do not know what to do. My Asperger's makes me paranoid if people hate me and always worried about what others think. It's starting to affect my schoolwork and this is a really important year for me next year ( highers, or A level equivalent). What do I do? 

Thank you x