Can't believe I'm dedicating a post to this, but that stupid Ska CD just feels like decisive evidence™.
This is from Asriel. It has to be. Ska is literally only mentioned twice in the entire game and it's Dess and Asriel's CD collections.
The case is still sealed, so obviously Dess did not ever intend to listen to it. Which begs the question: why is it still in her room? Just look at that pile of various instruments right next to the CD player.
Astute observation, and excellent summary, Kris.
If she didn't want that CD in her room, it would either be in pieces, in the trash, both, or at the very least hidden somewhere out of sight like Asriel's retainer is. (why do you have that? HOW do you have that?).
But no, it's just laying there with the rest of her CDs.
Never opened, never played, but a part of her collection anyway.
Because she can't bring herself to throw away a gift from that Massive Dork™ next door.