Friend with lupus obsessed with photographing my sister -hurtful

Gosh I feel like bursting in tears sometimes and sometimes I do burst into tears because of what a let down friend I made at school and one who I've not been able to shake off or lose touch with. She has gradually been doing more and more things to annoy me and just wish it was time she'd disappear out my life. She was constantly in touch with my sister but less so now since I kicked up quite a fuss by sending her explanatory emails about what she was doing to me and how low she was making me feel.

I just don't want to have to correct her behaviour anymore I just want to lose touch. I just wish she'd stop inviting me to old groups of school friends get together. I find them really annoying I just want to get on with my life. She has lupus and I know for a fact she expects me to help her through it and the only way she can keep my attention is to make me jealous by being obsessed with taking photos of my sister. It's ridiculous she's put over 100 photos of my sister on a social networking site - and it was me who sat next to her in tutor group every day for 7 years NOT my sister! I deserve more credit than this.