evil 2nd wife

i live in california but my parents moved to oregon 7yrs ago. my parents were married for 43yrs. mom died in aug.98 dad met a woman 16yrs younger than he, now 71yrs old the following may. she moved into his home in june and they were secretly married by feb. dad is an alcoholic, this woman has completely taken control of him and his assets. she has even had her name added to the deed of his house which he owns. she doesnt allow him to go anywhere alone or to get phone calls unless going through her first. he has lost all contact with close family and friends because of her. its almost as if he has been brainwashed. my question is there anything legally my siblings and i can do to prevent her from inheriting his estate? she obviously doesnt care about him. im assuming he has changed his will. we feel so helpless watching our father being taken advantage of. this woman has no assets of her own. its scary. because of his alcoholism we are extremely worried about his state of health as well.
thank you,