Supv on FMLA, dept falling apart!

We have a manger on intermittent FMLA diagnosis is MS, asthma and migraines. As a result of her frequent absences the nursing floor she supervises is falling apart and patient care is suffering. She is not in the top 10%. Is there any way we can legally transfer her out of the management position and replace her with a manager who will be present? It is creating unbelieveable problems in that she is out at least two days a week, sometimes/often more.
Comments
Hope this helps!
Do you still think we're ok in a transfer to an alternative job? I don't mean to split hairs, but also know that she's not going to take this well and has threatened legal action before!
Good Luck!!