She wasn't entirely sure what was going on with Harry, but taking the potion would help and she was sure he needed the air because he was hot and possibly running a fever. Although she would have liked it if Harry had carried her outside in a hold that wasn't displaying her bum for everyone to see. Of course no one would really see anything beyond her black knickers, but the concept still applied.
"Yeah I'm okay." she replied, "If you'll take that cloak off you won't be so hot. Your covered from head to toe in that thing. It'll help you feel better."