Most Helpful Girl
I don't see what the big deal is as long as she and the ex boyfriend are never alone together. If you're with someone and you get along with their family, that's great. But just because you break up doesn't mean you should stop hanging out with other people that you met through them.
In high school I had a boyfriend who introduced me to his friends and I introduced him to my friends. Our breakup was messy but we still hung out with each others' friends. It was weird and everyone thought so but we liked the people we met so we didn't stop seeing them because we were no longer seeing each other. It's like that.
Also, my most recent ex is still angry with me (and it's been over a year) but his mom still comes into my restaurant to eat and we're very cordial. He hates it but there's nowhere else in town that will prepare a veggie burger so there isn't much he can do.
Long story short, just because a girl has contact with the friends and family of an ex doesn't mean she will go back to him or even consider it. Usually a good relationship with the family is a reason to stay so if she got out anyway then she doesn't want to go back.