Fosamax.
If she is suffering severe osteoporosis, or is having bone pain from cancer mets, zometa is the right choice;
For prevention, I'd start with Fosamax, and keep monitoring her bone density besides cancer activity.
She will not be allowed to have any dental surgery once she starts bisphosphonates therapy.
Zometa can knock you out for a few days on first injection - other than that, it is a pretty safe and well tolerated drug