Cancer. Would it benefit her to take Fosamax (alendronate) or serm's or even take estrogen?

Clarification? What kind of cancer? Are you referring to cancer that has spread to the bone? Or to prevent it? There are a couple of medication used in metastatic cancer to the bone - zometa or xgeva (denosumab). Estrogen/serm/fosamax are not used in that setting. As for now- nothing is confirmed by radncomized study that we can use to prevent cancer from spreading to the bone (need more study on xgeva (denosumab)).