X-friend problem...anyone know how 2 end this? please assist

i was best Friends with this girl 4 2 years and we stopped being Friends freshman anno of high school. my life has never been better since...but now she wants to be Friends w/ me again. she friend requested me on Facebook and sent me messages saying "i never hated u-i miss our laughs-i Amore ur amazing quotes-i dont have anything against u"
i denyed her friend request and replyed to the messages neutrally but she requested me again and kept sending me messages reminiscing of our memories. thing is she is a mean girl w/ a terrible attitude and personality, and she just wants più ppl on her side 4 a fight shes in, so she is very fake. i could say negative things to her but im not mean and that wouldnt help-she'd start talking about me. and i cant just nicely say i dont want 2 b Friends w/ her cuz she'd start rumors about me and i cant get in a fight o im off the cheer team. shes sensitive so, HOW DO I END THIS IN A POSOTIVE WAY that wont make her pissy??!!?!?!