Dealing with role reversal

Hi, My Mom has had lung cancer for over 2 years and although they say she is in remission I have my concerns. She takes too many Xanax abd Vicadin and I don't know what else? She smokes too, she said she quit after siezures last week, but I think she is sneaking them. Anyway, I moved in to take care of her, and she is very resentful and spiteful, even downright nasty. She is moving and hiding things all the time, a real busy body, and now doing some bizare things like using shaving cream for mouse, or hiding things? I am worried, and she won't take suggestion, she sleeps all day, major depression.... I try and get her out, but she is pretty feeble. I am at loss... Dave