My friend is still dating this loser?

He has cheated on her soo many times.He told her he wants to bang her sister and he has texted her a text message that was intended for another girl on accident yet she still came back to date him. If this was me she would be so mad at me and say im stupid for still dating the guy. Now he has pics of girls on his phone and she dosn't trust him so she went through them he took them off but i bet he'll still have more and just delete them when they hang out. Shes saying shes tired of the games idk why she wont just leave him. I have been in this situation before but if it has gotten to like 6times we have broken up i would have been done. What should i tell her ??