Mother's Day (1) - S6.E22

Debra takes offense when Marie accuses her of being rude and the two wind up fighting and not speaking to each other. When Ray tries to make things better by getting each of the women to apologize to the other, he only achieves in making a bad situation worse. Then, the unthinkable happens (at least to Ray) - Debra decides she likes it when Marie doesn't speak to her and she intends to keep it that way.