HELP 😒😡

So I have this friend who I am pretty close with, and she's been really open with me lately. 
Here's the goss- she's been having relationship issues with her boyfriend for 6 months- long story short - she is over him, lost feelings, no spark you get the jizz. 
Her ex boyfriend recently became single and is now contacting her and that's not even the bad part! 
Yesterday he asked to hang out, of course she said yes, she kissed him as far as I know, not sure that's all they did but anyway she cheated on her boyfriend bascially. 
I don't know what she wants me to tell her?! She's never broken up with her boyfriends before, yet she's the type of girl who simple can't stay single!! She always has to be in a relo. Ffs. Rant over it just pisses me off 
Anyway the whole point of this rant is that i don't know what to tell her without sounding like a total bitch. I understand she's going through a hard time but I feel so angry because I was once cheated on and I just feel like screaming at her saying GROW SOME BALLS AND END THE RELATIONSHIP YOU LYEING WHORE! 
Fml.Â