By process of elimination it's Fluttershy.
Twilight would probably lock me in a magic bubble and convince me that I am dying.
Pinkie wold go all Pinkamina because I wouldn't find her antics funny. :okiedokielokie:
Rainbow Dash just wouldn't care.
Applejack wouldn't be too bad, but she can be a bit badgering.
Rarity could be alright, but I would be at her mercy for whatever fashionable blanket, hat, medical device, etc she would want me to wear.
Fluttershy would be at my beck and call, and yet quiet and would leave me alone if I wanted.