It's a very difficult situation, David, if your father won't take it seriously. My concern is that she has some kind of medical condition that needs immediate attention. Does she have a doctor? Has she had a physical recently? Maybe it's time to suggest she have one - and call the doctor ahead of time and tell him about your concerns. He can't share confidential information about your mom with you, but he can always listen to any information you have to share.

Also, see if you have a local chapter of NAMI. They may have some ideas.