In the earlier talking-head, Janelle had said that both Christine and Kody left the AUB. But, let's forget that for this segment. . . That way we can get Christine and Janelle to grift for their spinoff on their dating lives.
She can be both stupid and a liar. The bar for intelligence is pretty low for the Browns, and they're all delusional that they can't keep their own stories straight, much less follow others.
So in all their finger-pointing, rationalizations and denial, Christine & Kody's marriage dissolved because of the lack of the intimacy. Nothing about the children's best interest.