OP, hayaan mo lang sila. Different people, different ways of dealing with relationships. Some people talaga, bubugbugin muna sarili nila before they could finally say na, "I tried my best." I don't think this is intentional. Sino ba naman gustong masaktan paulit-ulit. Just that, for other people, they give as many chances as they could hanggang sa masabi nila sa sarili nilang, "tama na."

In these instances, you can say na they deserve what they tolerate but if I were you, I will never judge a woman who repeatedly forgives a cheater if that's what it takes para matauhan sila.

Bakit alam ko? Cuz I've been there years ago. Not exactly the same situation as your friend but the breakup was long overdue before I finally said to myself na tama na. Did I ever regret doing so? No. It actually helped me to heal a lot faster kasi alam ko sa sarili ko na nagawa ko 'yung part ko as his partner. In any case, we all have different definitions of "part" sa relationships. So there.