Does the entire friend group really need to ostracize the cheater after a breakup?

Q:

Hey all. Sooooooo, my friend group is in a major crisis. My friend "Marilyn" (they/them) and their partner "Charlie" (she/her) recently broke up because Charlie cheated on Marilyn. They had been dating for many years, I’ve never known them apart, only as a couple, all the way back to when we all became friends. But it has become sooo very obvious to all of us that the relationship was not working anymore and they were both unhappy. Marilyn wanted Charlie to propose and Charlie was dragging her heels. Marilyn seemed very bossy and actually low key controlling of Charlie sometimes. Not to say Marilyn is a bad person!! They’re a sweet as fuck friend, s...