Mom has two trusts. My sister had her sign a notarized letter stating that she can stay in house with all utilities paid until estate is settled.

I am assuming that the house is owned by one of the trusts... Who is mom's trustee?  Is your sister the trustee?   If so, it is possible that she might be engaging in self-dealing and breaching her fiduciary duty.  If not, then the trustee (if not your mom) could simply ignore that letter if the trust does not contemplate this action. If the property is in the trust, there really should be no "estate" to be settled unless you are using estate to refer to the trust property.  If the terms of the trust are that her kids become immediate beneficiaries of the trust(s) at her death, then the beneficiaries interests should supersede the letter from mom.   If mom doesn't remember signing then there could be an issue with her capacity to sign the letter to make it binding at all and could also be construed as elder abuse on the part of your sister but, for the sake of family unity, I would be careful about leveling any charges of elder abuse unless you first discuss it with an elder law attorney who can give you a better idea of the merits. I know you are here for an answer to your questions, but I cannot really answer your questions without asking you a number of questions first.  I would suggest that you contact an elder law attorney to get a better idea of where you stand.