The cute title for this Missa X vignette refers to lesbianism as something that you can catch, not a bad thing like cooties exactly.
So it's treated positively when step-sister Ivy Wolfe seduces sis Scarlett Sage. They make a cute team, and play very well together on screen, with Scarlett's initial reluctance disappearing in a nonce as it becomes clear that she's bicurious and has been protesting too much at the notion that her sibling is a lesbian.
