1. does she regularly take non-steroidal anti-inflammatory drugs (tylenol, motrin, advil, etc.?)
2. has she tried supplementing with magnesium? magnesium is a very common deficiency. i'd try 800-1000 mg of Mg citrate, malate or amino acid chelate (read labels, you do not want any Mg oxide) for several months and see if it helps. only possible side effect would be loose stools if she doesn't divide up the doses into several portions for the day.