Don't mess around wondering. Get a video camera on your grandma. Does she live in San Jose? If in San Fran speak to Asst. DA Richard Hechler, Special Prosecution Elder Abuse. 14 of the counties in California have special prosecution depts for Elder Abuse. They all vigorously prosecute elder abuse, as well as Florida.
It sounds like a classic case of undue influence. There are cause of actions both criminally and civily. Go check out CA PC 368.
Get Adult Protective Services involved. Though they are underbudgeted and often miss the financial abuse, they are your first line of defense.
I can't STRESS anymore, to get involved and to fight like a pitbull. The system is stubborn and blind. With Crawford v Washington weakening CA evidence code for elders, you must get the ball rolling.
If she lacks capacity, go through the conservator proceedings. Get a mini-mental exam (MMSE) Geriatrics. Trust me, I saw alot of people wait until it was too late. You think physical abuse is bad, financial abuse strips the OPPORTUNITY of peace and mind for the rest of their well deserved lives.
Keep on guard, knowing your adversary is the #%$ that he is, while you are doing everything to protect your mom, he will attempt to turn it around against you, i.e. "Look they want your money," "They are trying to commit you." He wants more than anything to isolate her from you.
Lastly, POA gives wide powers, Check what type of POA. There are different types authorizing total or limited powers. Check all property titles, etc. Beware of the Joint Tenancy tool for abuse.
Do me a favor and do something about it NOW.
DAM