As we've seen oh so many times, Laura's default reaction seems to be that since they don't know a blasted thing about being a farmhand, her city cousins have manure where their brains are supposed to be and she goes out of her way to say so. As I said before the last time this came up, she does so because she is tired of being asked to play baby-sitter because her idiot aunt and uncle can't be asked to spend a summer with their children without packing them off for specious and self-serving reasons.
What seems to escape the Pattersons as a whole is that Laura is simply the most forthright of the relatives who have little time for their bullshit; everyone else just smiles a plastic smile as they're forced to endure an invasion from the worst members of their extended family. As by way of example, her parents and grandparents make more subtle digs at her Uncle John, the idiot he married and the dough-headed children they have. In that, she's a lot like said imbecile hausfrau's own mother.
While it's true that Elly inherited her ability to worry about the improbable and need to throw her weight around from Jim, she inherited exactly one-half of Marian's personality: the part that's an obsessive-compulsive weirdo. The part of Marian that can tell shit from Shinola seems to have skipped a generation and wound up inside that awful Martian; the reason I say that is that both Marian and April can tell when Elly's being an idiot and both tend to say so.