I don't know what to do...

Sophie
So recently started dating a guy... Well kinda recently. Well there has been trouble with his female friend that is like family to him. She is young. Wouldn't date her at all. Well I knew she was lying about a shit ton. She lied about having leukemia, lied about wanting to commit suicide, etc. I told her and helped her because I wasn't sure about the sucide. Well ends up she was. One day later she decided to drop him and she told me to tell him that and I said NO. You tell him. So she did. Now she tell him lies about me. He doesn't believe her tho cuz we talk all the time. I'm on skype with him a lot. I feel like she likes him in a way. Idk but she won't stop messaging me. I told him about what she is doing and lying about. He told me thanks for opening my eyes. I don't get it. I was sweet to her and didn't mind her talking to him one bit but now it's like wtf is going on. He doesn't even message her but she won't stop messaging him. Like 100 a day. I can hear it going off on skype and him getting depressed.... He's also coming to see me soon but idk if I can take her messaging him and him being depressed. Just stuck and don't know what to do. Even think. Any ideas ladies?