Hi - Not sure why she's on Arimidex if her cancer is non-ER/PR-receptive, as Arimidex works to stop estrogen formation. Which is why it's bad for the bones. I would ask her doctor why she's on Arimidex. Tamoxifen has some very limited benefit for non-ER/PR-receptive cancers, so yes, she might try that, esp. since it's been shown to have effect even when it's taken many years post-treatment. Good luck - PJH