A new employee is often ill. Can we enforce a leave of absence?

Q: “We have an employee who’s been out for medical reasons for a couple of weeks. This is the second time she’s been out within the space of a few months. She is fairly new and we’ve tried to be as supportive as possible to her and her medical needs. I am now recommending she take a leave of absence for 30 days so that she can fully recover before coming back to work (should she be fully recovered before the LOA expires, she could come back earlier). She doesn’t want to take the LOA for financial reasons, and instead wants to come back on modified duty. Can we insist she take a LOA? Her job is essentially sitting at a desk and driving to clients’ homes when required, so I’m not quite sure what ‘light duty’ for her particular job would entail.” – Kosko, Pennsylvania