Legality on evicting friends?

My dad is vulnerable financially and emotionally since my mom died two years ago. He very lonely and at 77 yrs old its hard to change your life. He has a woman he met online that is suspicious of possibly golddigging to get his propety.She moved in after two weeks of meeting my dad. She is starting to talk about who is on the deed during arguments and she is mentally ill. Severe depression, now starting to drinkl. I am scared that she has an ulterior motive or that if my dad dies what can happen? He has no will, but has us 4 kids. If he dies can we tell her to move out? We are working on getting us kids on the deed of the house as well as doing a will. . He also has pulmonary hypertension and wears 4 liters of oxygen continually. and his health has declined dramatically after a year.