How do we terminate an employee who is medically unable to produce?

Q: About six months ago, one of our office staff had a stroke. She was off for about three months and returned to work two days a week for two hours each day. She is very limited in what she can do. The company has continued to pay for her health care even though she is not working full-time. The company can no longer hold this position, as she is not able to perform her duties. At this point it does not seem as though she will ever be able to return to work full-time or for more than four hours a week. How does the company terminate her without any repercussions?  – Marian, Pennsylvania