Ex girlfriend is trying to sue me for house I bought and let her co sign on after to living in or paying anything for a year . What are my options there is also a tax lien on the property by the IRS

Co/sign means little, except she has to pay loan if you don't.

Is she on or not on the deed, if she is on the deed, depending on how it is listed ( exact words) she will normally own 1/2 of the house

Let me see, loan on house, being sued by ex over ownship, and a tax lien.

Is there a lot of equity ? If not I would walk away and let them have it.