Very cute little game! I like the spooky atmosphere, and love the main character's design - especially the small details added to the animation like the changing of expression when attacking, or the bouncy little idle, the blinking of the eyes, and the secondary motion of the hair buns when using the vacuum.
I do think though, as other commenters pointed out, that the background can get a bit too busy at times, which distracts from the charm of the spritework. It can also get very hard to parse the UI against particularly complex background textures, like so:
Which is a shame, because there's a lot to like about the sprites.
Gameplay-wise, I feel like there's some room for improvement. Very often it seems ghosts will just pop up right in the middle of the screen, damaging me with very little I can do about it. It feels less like a test of reflexes, and more like a "gotcha" from the game, which rarely feels good.
I also feel like the vacuuming mechanic is underexplored, to the point I wonder if it's needed. As it stands, it's just a clunkier/slower way to get collectibles which I could presumably simply get by walking through. If there was more of an integration of vacuuming with the combat mechanics (like in Luigi's Mansion, for instance), I feel like this would be greatly mitigated.
As for the "meta", I liked the idea spending ghost ashes on the upgrade screen. I can imagine this being highly strategic with choosing upgrades best suited for the mission I'm going for, in a more fleshed-out, non-jam version of this game!
I enjoyed a lot about this entry, and feel there's a lot of potential here should the team chose to keep developing the game. Nice going!