The problem I have from this that isn't Elly's irritating habit of thinking that no one loves her or cares about what she does and will only think about being grateful to her years after she dies is that I don't see anyone benefitting from it. She certainly doesn't get a damned thing out of it. First, she loads down their plates like an idiot because she can't remember that a small child simply cannot eat an adult-sized helping of anything. Second, she gets pointlessly upset at them because of that witless "If they hate mushrooms, they hate me" belief of hers, she loses because she had the need to avoid left-overs beaten into her by a near-psychotic Depression kid mother with a worse case of OCD than she has and finally she loses because she wastes money buying more food than the family needs.
We also have to remember the children lose. Not only do they have to remind themselves that Mommy and Daddy are always angry at them just because they're children, Elly's need to trick them into eating stuff they hate for their own good teaches them that Mommy simply cannot be trusted, doesn't care what they think about anything and expects blind obedience to her brutal commands. Years of living with a bizarre and creepy narcissist with a persecution complex and an unhealthy relationship with food make them lose even more than she does by making them warped and crazy too.
Hell, even John loses. All he wants is the simple, humble fare his beloved mother cooked and he doesn't get it at all. He has to deal with his insane wife's endless experimentation with one bizarre meal after the next. Every time he suggests that they eat something not designed to disguise things, he gets accused to trying to sabotage her by making her life simpler and happier. How dare he try to fix things when she needs to be nailed to a cross to feel important. Next thing you know, he'll be asking himself why she needs to be paid an allowance like a damned eight year old!!