First, I assume that Canterlot Castle has its own medical wing, where emergencies - such as this one - can be treated.
Second, if the doctor is new or works night shifts only, she may not yet be accustomed to the idea of a dragon living in other parts of the Castle.
Third, the doctor is my friend's OC! As of now, she works as a Junior Doctor in one of the Britain’s biggest public hospitals and agreed to “play” small part in my story
My Little Pony - Friendship is Magic © Hasbro
"I was a stranger and you welcomed me."
"what you did for your brothers and sisters, however humble, you did for me."