@sentenza212,
Sounds super unethical to me and I haven't even checked any guidelines. She's taking advantage of a relationship in which he is vulnerable, to sell him her stuff. If he's seeing her through a hospital, contact them. If not, contact the Arizona Psychological Association -
http://www.azpa.org/ - and tell them what's going (and also go to them if contacting the hospital doesn't get you anywhere).
I would, if I were you, talk to my father beforehand, though. If he is getting good help from her then he needs to get a heads up that the side business is unkosher - and that you are looking to do something about that as you fear he is being taken advantage of.