Simply put, we're dealing with the same disdain for doing things that take mental or physical effort that has always blighted her life. She blew off University because she had to actually work, she blew off night school because it was hard and so on and so forth. Elly's past is littered with the wreckage of things that started hopefully only to crash into the ground hard because of her deep-down laziness. Were this not bad enough, we seem also to be dealing with an active hatred of people who do work towards a goal because she assumes that since she feels bad, they only did to make her feel bad. Since she'd rather not admit that her parents were right to praise Alan more sincerely because he did put in the effort because that means that there were people holding the door open for someone Fate assigned the role of "angry and incompetent also-ran," she must piss all over people who strive and succeed.
This is why John is a horribly incompetent dentist who deep down hates his job. This is why Phil makes a mess of the camping trip when he panics like a fool. This is also why we're going to get a steaming load of ordure about the horrible incident in which Rod's plane flipped over. Rather than be truly concerned, Lynn is going to all about how he sort of deserves it for having something she can never get because people who have things she doesn't are clearly being mean to her because the alternative is the scary, dangerous admission that she can't handle the character building words "You suck at THIS, Lindy!"