My wife has dementia and she went through the spitting phase for 2 to 3 months. She outgrew it like many other phases. It was horrible and gross while it lasted. Right now we are in the constant repeating herself phase. Says the same thing over and over couple hundred times a day. I would much rather have this than that terrible spitting.
Make sure you always have e tissues handy and when you see her gearing up, hand her one. If she has dementia, you cannot get her to quit. Unfortunately, this gross habit just needs to be tolerated. However, make sure she doesn’t have a physical reason. A trip to her dentist or an ear, nose and throat specialist might be a good idea.
If you find a solution I am interested.