(Strip Number 246, Original Publication Date, 15 April 1982)
Panel 1: It's late at night at the Pattermanse; as Elly and John sleep, we hear an off-camera "Cough-cough-hic-WHINE-MAMA!!!" which has the effect of getting Elly to awaken.
Panel 2: We next find Elly with her hand on a feverish-looking Lizzie's forehand and whining "Oh, no, Elizabeth! You're not coming down with Michael's flu too, are you?"
Panel 3: As she climbs back into bed, she tells John "That's all I need!! BOTH kids sick at once!!"
Panel 4: His saying "Huh?? I didn't hear you, honey; I don't feel very well" leaves her gobsmacked.
Summary: That's because the stupid cow thinks that her family got sick on purpose to destroy her ability to express herself; the idea that they aren't sick on purpose is not one that she can even formulate because it doesn't appeal to her repulsive vanity.