How can I protect my mother's money in the bank and securities from Medicaid if she ends up neading that.

I'm an only child and right now we have enough money in the bank to pay for what her long term insurance plan does not cover for about 3-4 years. In 2002, she gave me both durable and medical POA which we needed in 2009, but could not find them. So, we had them made again. About 6 or 7 years ago, my mother made me joint owner of all of her bank accounts with the right of survivorship. She's done the same thing with her securities. Since the middle of 2009, she has been evaluated as incompetent by both her neurologist and the nursing home doctor. I walk a strange line between being co-owner and being her POA as well as according to her will the sole inheritor of everything she's ever bought, been given or inherited herself.