What Causes A Painful Salty Fluid Discharge Between The Teeth And Gums?

Two years ago after receiving a tooth filling, my mother developed very strange symptoms. Let me start by saying my mother has fibromyalgia, so I believe the the symptoms are nerve related. She continually secretes a salty/foamy fluid from between her teeth and gums. Secreting the fluid is painful and burns. If she swallows it, it makes her sick to her stomach, so she has to spits it out all day long. She is taking pain meds to control the pain, and has tried several antibiotics but nothing seems to work and no doctors or dentists seem to be able to accurately diagnose or treat it. She is losing weight rapidly because it is difficult an unpleasant to eat. Have you ever heard of a similar situation?