My bestfriend is extremely possesive :/?

Ok so I recently became friends with a boy who will be known as C. Me and him are exactly alike and we really click and recently he told me that he really liked me more than a friend and I liked him as well. but my other friend who will be known as V dated him a year ago and only for a month and like ever since I started hanging out with him and doing things with himshe has been soooo posessive and it's really weighing me down and she is my bestfriend and so is he because I just like him alot and he understands better and is ten times easier to talk to and just a downright amazing person to me. but he has a gf and he has told me that the only reason he hasnt tried to kiss me is because of her and V keeps saying that he is going to dump her for me and I keep telling her that he is not going to do that he just likes me and she keeps telling him stuff apparently to convince him to stay with his gf and stuff and she lied to me and told me a lie about him that i found out later and just she is really possessive and annoying to be honest. she keeps saying stuff like "you are replacing me with him!" and "you are cheating on me!!T.T" and finally I just told her to stop it with the "Cheating on me" thing that it was getting old and she like got all bitchy and mean and I asked why she was mad at me and she said that she just doesnt vent and she doesnt know. I have asked her 20 times if she still likes him and every single time she says no. that she has lost intrest and I have had a few people tell me that they think she has a "crush" on me. idk... what are your thoughts on this? she is currently pissed at me sooo. what can i do to fix this?