... both prior to and after her shift to counteract some kind of serious gastrointestinal illness (don't know if it was bacterial or viral). Still worked.

There's a strong expectation to work through illness unless you can find a replacement for your role, which often can't be done in short notice. That said, one time I was so sick I almost passed out in the shower getting ready, and my boss cut me loose when he saw me at work later. Needed someone else to cover my assignment though, so fortunately someone was available.