No, you are both responsible if both signed. The lender doesn't give a flip who is living in it. If she signed, she promised to pay. Hopefully you would be able to sell it for enough to pay off the mortgage but if not, you would need to talk to your lender about a short sale unless you are able to come up with the difference. Depending on the lender, they may hold you both responsible for the difference or they may write it off. It isn't split in any way, you are both responsible for the full amount. A short sale will show up on both your credit report and hers, but not as bad as a foreclosure.
You are going to need for her to cooperate with you on the sale of the house and a short sale if she is on the deed.
This post was edited on 2/13 at 12:51 am