She would have had to pay rent and be there for more than 28 days to be a tenant. But Maine eviction courts favor tenants even when landlords are in the right based on the law. Landlords who show up to court hoping for a clean eviction, if they lack counsel and do not have a perfect case, are essentially railroaded into arbitration before cases go to trial. Housing advocates appear in court to manage arbitration before each case is even heard. (This is based on experience in Waldo County, but it's a state law so I assume it's similar elsewhere.) So if you got rid of her, you are good and change the locks and you should probably never let her back in the house ever again, or at least not until you're sure she has a place of her own and is settled.