This is why it was so damned easy to lie and say that the Nichols children were packed off to a Catholic school so that Lynn could elbow us in the rib cage about how backward and stupid Papists like Annie are. Having Liz end up marrying Christopher would mean Lynn having to draw a character without having a real person to copy from and unless she's churning out toddler jokes, she just can't do that.
It's also why Molly and Gayle had to disappear and move away. We not only got to watch that stupid pig Connie Poirier whine about their going into the dark and never coming back, it was a handy way to silence people who called the domineering old fool a muttonhead who stood around barking orders like she had any right to do so only to howl about WILD ANIMALS when their response is "You ain't my mother, lady; you're just Dad's latest girlfriend."
It's even why that tomboy Janice had to be defanged and then unpersoned. The alternative was creating a break-out character that would make people wonder why we had to watch some dumb housewife who was lousy at everything and complained all the time. This points us to the real problem Lynn has with other people's children: they represent an active danger to Elly's acceptability and prestige as a character. This is because while Anne might get angry and frustrated too, she knows something Elly seems incapable of admitting: children just got here and don't see what their elders see.
Elly's seeming inability to want to admit that people don't know things she does and know things she does not is not only why we see baffling garbage about children who say they're 'down there' because they're not at adult height, it's why Elly seems to think that her children are trying to argue her into submission. It's clear as crystal that when Elly starts in yapping about her her children argue and fight all the time, the dozy nitwit once again fails to even want to understand that her children cannot see things through her eyes and it's an act of futility to make them try. Watching other parents realize something a vain dunderhead can't because it 'diminishes' her and also because she's an infant who never developed properly would inevitably result in even more letters that have the theme "About Elly not being around children? GOOD IDEA!! She shouldn't be around kids because she sucks at parenting!!"