The context was it was a shitpost about a lesbian who's never been kissed, and no one knew OP's gender, so Velma was assuming that while trying to manufacture outrage on a shitpost.
Meanwhile Tanis was basically self-identifying as "bitches," and Velma seemingly contradicted her own stance that it might be okay for women to "reclaim the slur" by shaming Tanis for being okay with using the term.
It was pretty convoluted, but ultimately there seemed to be no point and it gave the vibe that Velma was just looking for a moral pedestal to grandstand on...