Question for a friend.

Friend and husband were living together in his home not claiming any tax credits as he earned to much she also works.

He leaves her for another woman, threatened to sell the house but felt bad so kept paying mortgage for her to live in as she has kids with him, She started to claim tax credits as a single claim, now his new relationship didn't work out so he has moved back in to her horror as she got used to having space from that control freak, she is sleeping in with one of her kids, he doesn't eat there it's just sleeping there, all his clothes etc are back in the bedroom.

What does she do?