Friend vs. Boy Friend?

Ok, so if you've read my previous questions, you'll know i really like this guy in my cl. I sit next to him in homeroom, math and reading, and he's my best guy friend. My good friend Shannon likes the same person is like obsessed with him. She acts like she owns him, and he doesnt even like her. They went out but he broke up with her because he didnt like her. Apparently she is telling my 2 besties who she follows around everywhere like a puppy that i keep flirting with him and he's flirting back. Shes Really mad at me, and im not supposed to know, but my friends warned me. This is the second time this has happened to me with her. She thought i liked her boyfriend and told everyone that i was trying to steal him and everyone hated me for a long time (until my 2 besties came along) That was 2 years ago, but we just forgot all about it and started over again. I dont wantt this to happen again. She did this toi my friends Kylie a couple months ago but she apologized (and it was the same person). I addmitt, i still did flirt, but i didnt even know she still liked him anymore (she layed low on the obsessiveness) And what do i do if he actually liked me back? Turn him down for a not-so-close-friend, or keep him and forget about her and what happened in the past, but have to go through hell full of rumors by her and have one less christmas present to buy lol.