1) A character says or does something really stupid.
2) Charlie Brown calls her on it.
3) The character successfully changes the subject by spouting a non-sequitur designed to hurt the Blockhead's feelings in the justified hope that since the "nyahhhh" is sitting in his stonach and burning, he'll drop the objection to Lucy's latest stupid remark or irritating attempt to rid herself of the little brother she thinks she had right of first refusal over.
This, of course, is designed to shield herself from having to feel bad about herself; the fun part of dealing with her is that she's amazingly thin-skinned. The instant she starts thinking that the people around her don't one hundred percent agree with her inflated self-image, she starts hollering about how mean-spirited they all are. This sort of shenanigan is what makes me feel that had the strip happened in real time, she'd have ended up telling Frieda that she loves her children but doesn't particularly like them.