Lol, to be honest, your scenario of what Delora could have done instead (telling Lucette bad things will happen if she doesn't change, then orchestrating said bad things, and doing this repeatedly every night, making her paranoid) is way worse--that's straight-up psychological torture/warfare 😂
Meanwhile, there's precedent in actual fairy tales for curses to have been used to teach people lessons to help them change, which Delora even mentions in the story 😅
I admit that in the early routes (Rod, Karma, Rumpel) you don't see as much of her so you mostly get her mean comments, but she's also trying to play "bad-cop" to Parfait's "good-cop" in order to prompt/goad Lucette into changing, and her relationship with Lucette progresses much more than that in Fritz's and Waltz's routes.
Therefore, I don't think it can be reasonably said that Delora is worse than Lucette's mother, who literally murders people (including Delora's daughter, who was a young child) and brainwashed and abused her own child 😕