As we saw with the "Let's angrily nail a pencil to the wall because we can't keep stationery in a drawer like boring, ordinary people" strip and will see with the "let's get all defensive when people ask why we shave sheets instead of buying more expensive ones we can easily afford" strip, Elly shares a certain trait in common with Hilary Forth in that she's someone with a can-do attitude about some things that simply cannot be done. Things, as by way of example, like trying to talk Farley into doing things because she simply refuses to admit that he cannot generalize to save his life.
What generally ends up happening in most situations is that Elly witlessly blunders into a situation with an easy solution and solves it in the most ludicrous manner possible. As by way of example, most people would think nothing of buying pencils and pens by the boxload and keeping them somewhere they remember; Elly sees that as being an unfair and wrong solution because it's not the one she would adopt. Buy pencils in bulk? Preposterous, says she! She should have the one pencil where she needs it and have sole use of it because that's how she wants things done.
This excessive love of bad ideas because they're her ideas and belief that being asked to be practical means that they hate her and don't want her to be happy ever tends to bleed into the rest of her life. Case in point: when Lizzie mislaid her glasses on the beach, the reason Elly wouldn't let her be anything other than a selfish child who wanted to hurt her poor mother by making her buy glasses in bulk is that someone who hates her and wants to laugh at her for being stupid forever made an "impractical" suggestion about how office supplies can be bought by the box-load. This leaves us with someone who has a crazy, stupid person's idea of the possible running her fool mouth about having to live in a real world she never inhabited.