My 89 year old independent mother-in-law started low dose Arimide...

My 89 year old independent mother-in-law started low dose Arimidex after mastectomy 6 months ago. She experienced sever bone/hip pain (requiring a middle of the night ER visit). She was advised by the oncologist's office to discontinue Arimidex. Several weeks after stopping the Arimidex she began to have night sweats, becoming increasingly severe.. She is uncomfortable, to say the least. Is this truly a side effect of stopping arimidex? Have others experienced this side effect post arimidex? Should we look into some other cause?