My best friend is in relationship with a guy for almost 5 years.

My best friend is in relationship with a guy for almost 5 years.
She is extremely loyal but the guy has cheated her many times, disrespects her in other words he is standing red flag 🚩
She caught him cheating many times but every time she becomes angry,sad & share everything with us and we suggest her to breakup then the next day they are back together and we feel we are like villains of her love story
Whatever he does a simple sorry can make her forgive him
We have tried everything to make her understand that she deserves much much better but still she is madly in love with him and even fight with us sometimes for him
Hope god make her realize soon what's right for her