She has a weak immune system so she's always getting sick.

She has another problem. Then another. Then another. It's been this way for pretty much 2 straight years. When she's here for the most part she does good work and gets good numbers, but that's the problem...she's gotta be here. I encourage everyone to take time off to re-charge and I've rarely ever,,,,in fact I don't think I've ever said no to a PTO request.

Then has mental health challenges (of which I try to be especially sensitive too).

As a supervisor/manager how do you or how have you handled these situations?

I work pretty closely with HR on this, but curious on your approaches.