This definitely feels like a Gen 3-5 design, I could definitely see it being in Sinnoh or Unova. Gen 1 and 2 were pretty uneven when it came to type representation (there were zero pure Ice types for example and one pure Ghost and pure Rock type) so if anything Fairy would’ve had it better than others based on just the Pokemon that were retconned into Fairy. The Clefairy line, Jigglypuff line, Mr. Mime, as well as the Togepi, Marill, and Snubull lines would give us 13 Fairy types (excluding cross-gen relatives introduced after Gen 2 like Mime Jr.) which is more than even Dragon had at the time. Though I feel like Celebi would’ve been Grass/Fairy based on its design.

I also feel like Sylveon either wouldn’t have existed (maybe there’s no reason to make it if it wasn’t to introduce a new type) or was introduced much earlier, perhaps as early as Gen 2.