I should think that the best example of her inability to understand what's actually happening because of a nebulous grasp on what people are actually thinking would have to be when Lizzie mislaid her eyeglasses. As I've said a lot of times before, Elly totally ignored how bad Lizzie felt because, well, Lizzie's carelessness was a minor inconvenience and therefore a deliberate attempt to cost poor her time and money. It doesn't matter that Elly herself is forgetful or that John tried to explain that no, stupid, your children don't want you to buy glasses in bulk to ruin your life because they hate you, Elly would not be moved. To this day, despite the fact that she herself forgets her own reading glasses every damned place and it's never her fault, dimwit Elly still thinks that Lizzie was trying to do something bad because she hated her poor mother because she can't understand why people would make good faith mistakes that hurt her if they aren't trying to ruin her life. She also can't understand why her children took years to stop seeing her as a judgmental dingaling who lives to leap down their throats because of that whole inability to understand what the consequences of her actions are going to be.
THE signature example of that failure to anticipate the consequences of her actions ends up with her in the driveway screaming NO!!! at John while wielding an ice scraper as if it were a scepter of failure and stupidity. Just as Mrs Gagnose Meddleschmirtz oppressed POOR Elly by suggesting that she's making an ugly fool of herself, John was bad for not immediately understanding that Elly's car needs to be in the garage despite the fact that it was her stupidity and spinelessness that allowed Mike and Liz to pull the hovercar in the manger stunt in the first place. If John wished to court brutal death, he'd have asked her the evil and wrong question "What did you think was going to happen when you just let the kids freeload off of us?" because she doesn't want to admit that the answer is that her adult children are the same clueless idiots they started out as.