I'd certainly seek advice from the Dogs Trust. It's unfair to your own pets to take 2 large dogs in to your house. Also, when your daughter decides it is time to find a place of her own,she will have great difficulty finding a rental home that will accept dogs , doesn't matter how well behaved they are.
From the sounds of it, her ex partner just wants her and anything to do with her out of his life, having been through something similar, I can say that if he can find something to blame her for or hurt her more , he will, including who has their pets. Otherwise there is very little reason, in my view why he can't still take care of the dogs and allow her visitation rights!
Sorry, but you are going to have to be tough with her, however hard it is as it is your home. If no other friends or relatives will take in the dogs, they may well have to be rehomed.