I mean,  if you think about it, Terezi is following the evidence well here.

Her past cosplay/larping outfits and supplies stored safely while the rest of her plushes destroyed?

Nepeta’s body in her Nick Cage Corner, along with blood written in her precious ancestor book

All of this is very well crafted to make Terezi think it is Vriska. But, there are some things that Terezi has missed in her investigation.

She didn’t look into the body’s form/deaths (as messed up as that is to look closely at a dead body). Terezi could have seen Nepeta bludgeoned to death, something that Vriska doesn’t really have as a weapon

If she cared so much about her ancestor, why would Vriska tear out a page from her book? That is her ultimate treasure.

Are you going to talk about the horn pile? Like, why would Vriska block the door with a horn pile? She has no horns. She would use 8 balls rather than horns.

AND THE PUPPET KEEPS MOVING, YOU MIGHT WANT TO LOOK INTO THAT ONE TEREZI!!!!