Nah, I think it was clearly suggested there's another person in the 4th bed when they were in a hospital. Was she really sick, she would get a check-up already and it would be stated for the show to make her more depressed. And a doctor would probably say something to a potentially dying person, not flirt with her.
She can have a stress related symptoms.
It is a plot device, but a good one. She's reaching important realisations as if she was to die. It gives her an extra spur.

I agree - plot device probably. Feels more like a "learn how to live AS IF every day was your last" kind of story rather that a "living life knowing every day might be your last" story. Also I think the point made by namopanik that if it was real the show would confirm it 100% and then milk it way more is probably true. So I'm like probability 90% not-sick, 10% sick. (if she is sick then that doctor is like etically waaaaay out of line)