There are others here that apparently know more than me....BUT if she has not put it through probate, I do not believe she has legal claim....UNLESS she was joint in all his accounts....she just might have had his estate whittled down into one or two accounts, which she was co signer on, in which case you're screwed, unless you can prove the incompetence...which will be nearly impossible, as I would see it...from what I've read here....was there a house???? who's name was on the deed??? lot a work remains....typically homes/land are held jointly, with right of survivorship....do not know what your dad's state was...