My mother has excessive salivation and a sore mouth. Has anyone else experienced the same thing?

My 89 yr. old mother has been suffering from this for almost 2 years. I've read about burning mouth syndrome and water brash. This can be caused from Acid Reflux. She has had an endoscope which showed inflammation in the esophagus and stomach. She doesn't like to take medicine and has only tried prescription Nexium and Prilosec for about 3 weeks at a time. I get her to take it but then she says it makes her mouth worse and quits taking it. She doesn't eat much anymore because of her mouth. She gets so depressed and upset because of it that she says she just wants to take something and go on and die. This really upsets me and I don't know what to do. I want to help her, but she is really stubborn and refuses to take any medicine except her blood pressure medicine. I am about at the end of my rope so if there is anybody out there that has any suggestions I would greatly appreciate it.