SPOILERS UP AHEAD. ONLY PRESS VIEW REST IF YOU ARE FINE WITH SPOILERS.
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I am unsure if the dialog is actually Dess talking. It sorta makes sense, but one detail stood out to me. They specifically mention there being one bed and a beanbag chair. I went and checked, and yes, Chara's bedroom has one bed and a beanbag chair. Now is this Chara? I don't think so, no. I think its either Dess, Asriel, or Nebby.
If this is Chara's room, Asriel would've been one of the few people who would go in there. The soundbite of the talking doesn't exactly sound like Asriel, though.
Nebby has some strange connections to Chara's room, and so far is the only one (besides us) that has gone in there (Got the dresser key and catches us using the dildo in the second round reverse riding.) Some of the speech patterns also follow Nebby's dialogue, such as the use of pet-names. Most of the drawings on the wall fit Nebby more than Chara, which is quite strange.
I only see Dess being the one talking if it's Asriel she's talking to (Dessriel). It would explain the location and how there is a connection between Deltarune and Undertale. I also believe that this dialogue does fit December's personality, at least as far as we have learned.