Either she or her son have no idea what they are talking about:1) Only the government can use "eminent domain": it is for the government taking property for a publlic project (like a highway, a damn, an airport, etc.). 2) "Adverse possession" can sometimes be sued by a non-owner to take over property that the non-owner otherwise has no right to, is using in an obvious way (so the owner could discover them and take action to stop them), and have been doing so for years. But someone who already has rights to the property, like a co-owner, cannot use adverse possession against antother owner, since adverse possession only applies when the one trying to take the land has no rights to use or occupy the land--but clearly, a co-owner does have such rights. She may be able to sue your father's "estate" for the money he should have paid for taxers, utilties, etc. but did not, but she cannot if the estate has already gone fully through probate and been settled. Even if she could do this, she can't get any money personally from your sister or you--only from the estate, or money (if any) left behind by your father.