Under the laws of all states where there is a situation where a piece of real property is jointly owned by two people one of the owners can secure a loan with his or her ownership interest in a given parcel without the other owner's consent provided the lender who will be secured with this fractionalized ownership interest agrees to such. there is nothing illegal as to what you have written but such loan and security from a practical matter usually does not happen unless the loan is a private loan.If your mother's signature on a document was forged, then she is not obligated under the law on the document she allegedly signed.