I don't know the whole story. but from what you posted I'd say keep paying and tell your in-law that you'd feel better about completeing your responsibility. and at the same time thank the father for continueing being responsible for j. thank her also for the offer but tell her this feels right to you. besides, if you don't really trust her then she may try to pull off something shady later on and say you never paid. she may hold it over your head at some point.