Not, of course, that she'd do either of those things even if she actually approved of something that her children were interested in. I'll get to why Elly hates everything her children like later. Right now, I want to examine Elly's stupid fear of making her children feel as if they have a chance of succeeding at things. My guess is that if someone were to ask her why she was sparing with the praise and liberal with criticism, she'd make some pious speech about how praising children leads directly to them becoming vain and entitled. She might even use poor Becky as a straw spoiled princess. The way she sees it, if all she does is nag her children, tell them that every single thing they do disappoints her and threaten to take their privileges away if they fail, they'll be humble and thus fit company.
The real reason that she does this is that Elly seems to actively hate the idea of enjoying life. It looks to me as if she has an instinctive dread of genuine happiness because deep down inside, she realizes that if she were ease with the world, she'd have to face the humbling knowledge that most of the things that bedevil her were never as important as she thought they were. Worse, she'd have to mourn the millions of lost opportunities worrying over nothing and falsely believing that her children hated her and wanted to ruin her life stole from her. Subconsciously, she's trying her damnedest to make sure that no one else is happy or care-free either lest she look in the mirror and see a stupid killjoy who made herself miserable for nothing. Publicly, though, she sees herself as helpfully preparing them for a world that isn't going to cut them a break.
The disturbing but predictable end result of all of this is that while discussing April's selfish refusal to have much to do with the family that loves her, Delusional Idiot Elly is sitting in the Tiny Train House telling her fellow complete failure as a mother Connie that if she'd nagged, berated and demeaned her children more, they'd have accomplished more. She simply cannot connect her reign of negativity and the fact that her refusal to do anything like say that she's proud of them has bred two apathetic, pessimistic loser children who can't cope with adult life and therefore must let their horses get owned.