Husbands Sister will not sign a Quit Claim deed!...we are stuck!

help! this is definitely a sticky situation. a few years ago, my mother in law had gotten sued, and they put the house that my husband and her were living in into foreclosure to pay. my husband decided that he would put buy back the house, and put the mortgage in his name. the title however, was put into him and his sisters name. long story short we got married and we are living in the house now. he has since had a falling out with his sister. she refuses to sign a quit claim deed that we drew up. we went to refinance the house because the mortgage is so high, and the bank needed her signature for that too which she refused to do! we are now stuck with a house we really can't afford and wasn't to really just get out of here and start fresh with no ties by ourselves. what can we do? we live in ny. thank you so much for your help!