any solutions ?

my friend keeps going back this boy that's most definitely no good for her and i don't know what to do . she is the nicest person ever but whenever she get with him she just so rude and its annoying .. i let her momma know bc they put up a front while around her and she tried talking to her but everyime she gets back with him she says "he's changed" and her attitude gets worse . I'm thinking I should tell her she needs to let him go but I don't think she won't listen to me and its getting to the point where I font even wanna be her friend ..