What is her problem?

Okay so me and My best friend have been hanging out alot more lately and She has made other friends in her cl too!And there is this other girl in her cl that thinks that her and my BFF Are like the bestest friends and Blah blah Blah But my Bff doesnt think the same about her! So when my BFF was at my house when the other girl called and asked to hang out my friend was like cant sorry im at Lauras house.the other girl then IM's me a few days later Yelling and Blaming me that my Bff isnt hanging out with her, she says i told My BFF something that made her hate the other grl... I was like i didnt say anything and she keeps accusing me of all this crap! And after she has said all this crap about me and to me she all of a sudden IMs me and is like Omg Guess what Im going to open gym too!!!!! want to hang out there? IM like NO!Then she accuses me of Prank calling her today when i was at softball tryouts and a bday party all day!Someone Help!I just cant stand her!