There's hardly a more YMMV situation than the one you intend to enter. I'd be positive and like to think that TSA will be understanding, but if it comes down to a full patdown and god forbid a granny style strip search, there'll be not much you can do except to be by her side and act as her advocate. On the plus side, almost all of the alzheimers sufferers I've ever met are very easy to deal with and are willing to go along with most situations without much fuss. Go into it with the attitude that everything will be fine and it most likely will.