At worst it was a financial transaction.
(There was a line from the evil villain on Devious Maids last week: "No son, I didn't rape her. Don't be ridiculous. You can't rape a whore.")
Loving sexy mistress in exchange for the elevation of the well being of her husband and children.
(That's why everyone in the real world drones goes to work in the morning. Well "everyone" is not a mistress, but they certainly exchange the doing of unsettling things for the well being of their loved ones.)
Here's the problem.
Meru and Dukat were both delusional.
They both forgot that she was being paid to pretend and just got on with it.
She was weak, and he was crazy.
In exchange for the fancy life Dukat was giving her, she forgot about the concentration camps and the resistance living in caves fighting to free Bajor.
That was the point of the story.
Kira's mummy was a dirty no good collaborator.