Pushing this aside, reviewing their past, this makes more sense.
They still murdered together. But after Vriska killed Aradia and Terezi punished her, Vriska tried to be better by making a body with Equius as an apology. With Vriska around, Terezi had confidence and didn’t fall into a self-doubt spiral.
They honestly work a lot better as a team, and moirails is a relationship literally about “checks and balances” which was what that whole vengeance thing was.
So I guess it was…pining? back then?