Is it though? “Case files” is in Showtime’s episode synopsis for it but it seems like it’s still following the titling (or lack of) of the previous episodes (Part 1, 2, etc).

I could swear I wrote Shelly, I was even looking at a few other articles ex. https://www.independent.co.uk/arts-entertainment/tv/news/twin-peaks-amanda-seyfried-twin-peaks-character-shelley-johnson-daughter-bobby-a7772811.html where it was plainly staring back at me but for some reason I guess I focused on the question too hard and wrote Norma. Thanks for noticing that, as I sure didn’t.

Isn’t she Shelly’s daughter?

Apparently her being Norma’s daughter is a pretty common assumption among reviewers, but few (if any) elaborate on how they conclude that (I suppose it can be argued from context of conversations in that portion of the episode that she’s someone close to her and they just assume based on the age difference that she’s her daughter).