if I am honest, you have sorta answered your own questions. There are two things that stand out for me here:

1.) Your job and your health
2.) Your on your 5th or 6th date

I personally wouldn't risk my health for her, also doesnt it send the wrong message that even tho she is ill you are desperate to go round. Also you have had quite a few dates, as you said, this isnt a flake. If she has said, I will see how I am tomorrow, it sounds like she has the value and authority. I would text her and say "that you cant risk getting ill and you hope she get better quickly" and then reschedule for another time. I cant imagine her not wanting to see you coz you cancelled, coz she was ill.

Thats my 2p's worth.

Tom