She has reached background pony stage four.
Stage 1: Discovery, marking the character out as unusual or interesting.
Stage 2: Naming, usually follows shortly after stage one.
Stage 3: Fan art, often accompanied by anthropomorphic art.
Stage 4: Complex fan works, including animations, Tumblrs, fanfiction, and anything that requires a great deal of time and/or commitment.
Stage 5: Relationshipping, can include romantic pairings, friendship, enmity, or any combination, the main point being that the character's interaction with the official cast.
Stage 6: Fandom consensus, which occurs when the fandom comes to a general agreement on the character's traits, personality, and behaviours. Other characterizations and/or names will either be forgotten, merged together, or explained away.
Stage 7: Official recognition, when the creators and/or Hasbro recognize the character's existence, this step may or may not involve an "official" appearance in the show.

There may be some overlap between some of the steps, and a character may not follow all of the steps in that order, and likely will not complete the whole list, but I think that this fits in with the general trajectory that a recognized background character will follow.

I must say, if nothing else: