Whose the eviler in this hypothetical scenario?

You have a boyfriend and a girlfriend. They're head over heels madly in love. They have a plan to rip off another girl. Only: the girl they we're going to rip off starts sleeping with the boyfriend well ahead of time. This girl is absolutely mean, sadistic, and brutal to the girlfriend in question. The girlfriend hates the girl but finds 100% complete solace that she at least has a boyfriend. The girlfriend has no idea that when they're at the house the outside is soundproofed and/or otherwise visionally as well. When the girlfriend is right close next by: the girl and the boyfriend (who hides it so infinitely well) have wild, ravousness, absolutely absolute diabolical hardcore in love sex in the hottub. The boyfriend still acts like he's the boyfriend of the girlfriend and his usual, ingratiated, normal self. However, this has been closely and decisively going on.