There's a large amount of fics involving cadance having been a changeling all along, enough fics to warrant her own folder. And in case someone wants to say "Show me some proof" I would say the following to them. I can't because there isn't a folder for it! You can't exactly do a tag search on "cadance was a changeling all along" because that's what groups are for.

Cadence is folded under Alicorns, since the stories involving alicorns are so rare.