Notice how in this episode, Miles reacts with concern for his wife. He goes along with things while desperately trying to to save the woman he loves. He constantly believes she’s in there and wants her to fight it.
Now compare this with how Keiko acted on the episode of TNG when Miles was possessed by an alien entity. Abject fear. Disgust. Even when a part of O’Brien seems to surface when he recognizes her and is clearly struggling, she does nothing but cower and scream at him to get away from her.
In short, more evidence that Keiko is an awful wife to O’Brien and seems to despise him.