It sounds like you have two good relationships, but sadly these two individuals don’t share a healthy relationship with each other. This can at times make you feel guilty, sad and even stuck at times. First things first, it is necessary to make peace with the fact that this situation may take some time to get back to normal.
At times, people with different personalities do not get along. Take a moment and try stepping into each of their shoes. Consider the feelings of everyone involved, view them as individuals, and accept that you can understand them, but surely not control their feelings. Spend time with each separately, let them know that you love them and choose them both. Insist on not picking any sides. Do not allow either to speak ill of the other, as this isn’t expected from you as a daughter and a wife.