What do you think of this girl?

I just read a 'agony aunt' column in a UK magazine which described: How there are four boys, in a university band. This girl 'Mimi' was in a relationship with one of the boys for 5 years. The whole band was very close and she was friends with all the members too. Of course, they are all living away from home at university and she walks in on her boyfriend cheating on her with another girl. She is horrified but has no where else to do and stays with one of the boys from the band for a few weeks before returning home and now she is having so much abuse and name-calling thrown at her. I was thinking, this seemed perfectly logical she was friends with all of the band and he was cheating on her - so why were people being so rude to HER?