Engaged sim without the adultery trait who finds another sim very unattractive is not rejecting them

[Idontlikesand1]

I have several sims who won't have sex because they're in relationships, but this sim in the household with the repulsive trait and being very unattractive to my sim was supposed to get rejected for story purposes, but my sim said yes without question!! 

 

Is it because they live in the same household or is this an error?

[Husk]

Depends on how well the Sims know each other, looks aren't everything.

[Faolon]

Do you have the cheat on that makes it so sims accept everyone?

 

Or, possibly, do you have Eco Lifestyle and the game passed the Free Love thing? That usually makes it so NPCs flirt with your sim more often and nobody rejects any advances.