In law drama

Ladies so my husbands mom opened a credit card under his name and he had no idea about it until I go to the bank and they inform me. We are trying to get a loan for a car because what I’m currently driving isn’t safe for our son. She got a credit card under his name with a balance of 25k. He is military and because of this his credit is pretty great . Buuut because this is “his” first credit card and the available balance is so fucking high she fucked up any chances of us getting a loan with a low apr . So now I’m heated we can’t get the car we’ve been saving for without a loan ripping us off, she involves herself way too much in our marriage and now this ? My husband is deployed so he can’t do much ....I don’t know what to do