Huh. On the one hand, FL did something that would warrant revenge. On the other, it's not her fault, it's the cheating husband's. On the third hand, she's had sex with a man that's not the ML and quite recently too, which I cannot overstate how much that's a game changer in these stories. And on the fourth hand, we have the old "what a slut; she compels me tho" HQ goodness where the ML wants the FL but doesn't respect her (or his sister, for sleeping with the same woman her husband cheated on her with; wow).
Verdict: none of the men in this story (except the dad, in another twist) are worth it, everyone should avoid them.