My friend is a whore?

So, my friend is always texting either my best friends crush or mine. She has a boyfriend too, who she cheated on with her cousins boyfriend (not her cousin! her cousins boyfriend) so I accepted it because thats my one of my best friends but i really like this other guy who was her friend at one point and when i told her i liked him she was all over him and my friend lila has a boyfriend which is her ex and all she does is text him and talk about her old relationship with him, and when my friend lila founs out she almost wanted to kill her. She doesnt respect anyone and i dont know what to tell her. Any help?