My ex-girlfriend is threatening to sue for equity in the house that we had purchased together. Her name is not on the deed or mortgage.

Under Wisconsin law, a non married person in a marriage like relationship who acquired property together during the relationship, can sue for equitable relief. The leading case in Wisconsin is Watts v Watts. She is not afforded the protection of the family code chapter 767, which means no alimony and no 50/50 presumption of the estate. The court has discretion to determine her equitable share. Title to the property is not outcome decisive and doesn’t resolve whether in fairness and equitable grounds you get to keep the house and she gets nothing out of it.