I'm looking for that collection. (I don't think it was an anthology or had more than one artist. Very unlikely.)

More clues:

It had at least 3 chapters, but was still clearly marked as either a oneshot or a series/collection of oneshots or shorts. Seems the author had intended to leave it be but went back to it?

Was posted on one of the bigger manga aggregators. I don't think it was on MangaDex. Very possibly KissManga?

First oneshot had a guy who works at an animation or manga studio and dreams of a talking cat. There was a scene where he talked on a train with the cat.

Then his prodigy female kouhai quits. And he dreams she turns into the talking cat. The dream is in set in his room, and I think during it she turns back human while lying on top of him, probably naked. But it's played for laughs, not ecchi.

Second short (2+ chapters) was about an indie musician/singer and her flatmate/friend. One of the girls may have been involved in domestic abuse (victim) in the backstory.

There's a scene where one of the girls fixes up the other girl's make-up and wardrobe to lift her spirits.

Cover looked close to this (Yakedo Shoujo Shiina) (Yakedo Shoujo). But with a wavy dark blue-ish background, sort of gave a (glossy) watercolor feel.

Thanks a lot!

Cleaned up details and added some new ones 😀

Edit: Mahou ga Tsukaenakutemo