(Strip Number 1262, Original Publication Date, 12 March 1988)
Panel 1: We find Elly at Megafoods whining to Connie about how she cannot stand the state of Mike's room because every time she passes by it, she wants to scream.
Panel 2: Connie tells her that if he tidied up his room, Mike would be conforming to her standards. By living in a pigsty, he's proclaiming his independence.
Panel 3: He's trying to show her that he has his own mind and is a separate, unique individual.
Panel 4: Since both of them hate THAT idea like poison, it's no surprise that they agree that their ungrateful brats are all alike.
Summary: The reason behind her angry bellowing has, I should think, a lot to do with her 'refusal' to get angry with Mike for pointing out that she made a hash of a costume that would get him laughed at; simply put, the vain dimwit takes every Goddamn thing as a referendum on whether she's loved. Since Mike wants to keep his room his way, it stands to unreason that it's he hates her.