Adorable, a wife that is suitable for their son, SHOULD be a good daughter-in-law for the mothers, IMO. If she inherently would be a bad DIL, then she probably would not be the best role model for the children the son will help bring into the world. There is suitable, and there is suitable. Not everyone can love her DIL and not every DIL can love her MIL, but there should be mutual respect shown to them, or the son will be caught in a tug of war between them.