I don't have any experience with back surgery. I am very glad to hear that she considers her MS mild. I am sorry to hear that it causes walking problems. As long as the doctos and nurses label her a "falling risk" while she is being treated, she should be fine. She needs to make sure she has either a wheelchair or walker during recovery. She will need PT. I am sure her surgeon knows about
her MS.
The surgery shouldn't be a problem. People with MS have surgery with few or no complications. She just needs to avoid falling. Injury on top of MS and her other problems may create some real problems. I wish her the very best of luck.