How do we deal with a mother with paranoid psychosis who is purchasing property?

My 75 y. o. mother-in-law is diagnosed with long standing paranoid psychosis and is in contract with a realtor for purchase of s 2 story house and has bad arthritic knees. The house is abut 35 miles from us verses less than 10 miles. One son is an orthopaedic surgeon and the other is a bankruptcy lawyer. What do we do? She is making unrealistic decisions and often makes statements that are not true. "Everyone is stealing from me at Rossmoor, they are putting something in my condo and knocking me out. I slept for hours. They are giving my dog diarrhea and are trying to poisin him. Those people are stealing my blouses and the toilet paper etc. etc., I am so tired of this...." I feel these realtors befriend her thinking that they are going to have some big business. It is obvious to most "normal" people that she is "off." What do we do? I am the daughter-in-law ( a nurse and a realtor). Both sons are angry, frustrated and I think emotionally drained not knowing what is the "right thing" to do. Also, she has seen a psychiatrist and she is non-compliant taking medication. Roberta