I get it now, I finally get it.

FRIEND is one of Noelle's cats from CatPetterz that she'd torture and abuse and mod. It's been established that she had a cat that made you LOSE points, and it's also been established that she's a freak that loves secrets and evil routes; aka the perfect genocide route player.

So the reason FRIEND took over Dess and is tormenting Noelle is because she wants to teach her that her actions, even in a fantasy world, have consequences. If you lose the fight and Friend wins, he extracts a zip bomb into your computer and crashes the game.