User blog comment:DxCx4vr/How long was Duncan cheating? SPOILERS/@comment-1756703-20100809183415

She had Duncan on her mind when she was in the confessional, so that's why she said his name. Like she said, it was a slip of the tongue. I don't think they had anything going on in TDA. After all, in The Aftermath: II, he was seen thinking of Courtney.

But who knows, maybe they did have something going on back then.