Loretta,
There are at least two prescription drugs that she might be able to try -- Salagen (oral pilocarpine) and Evoxac. Both of these are used to promote saliva production; in some people they can produce side effects, so it's important to watch for those. I've been on Salagen for 15 years continuously, and for me the benefits outweigh the negatives.
Also, the Biotene mouth products (nonprescription) have helped many people on this site. The line includes mouthwash, gel, toothpaste, spray and chewing gum. You can find them at many of the major chain drug stores and Wal-Mart.
Cathy