It is up to you to call or not to call a mental construct in your brain Pinkie Pie. My point is that there is no physical mare named Pinkie Pie which we can consider real. The only thing a person could have is a mental construct in the brain based on the information from the show, fan fiction and other sources. We can name it Pinkie, because writers of the show scripts and some other people would do so. Or we can do like you suggest, use the name only for the whole body of knowledge about Pinkie Pie.
P.S. And there is one thing we shouldn't do: dispute definitions.