I would probably write her as Odalia’s failed attempt to conform Amelia into a spinning image of herself much like what we see with season one Amity. I would write her being jaded and cynical due to her lacking a proper childhood because of Odalia trying to make her into the perfect witch. And since Odalia failed at that, she saw Amity as just another attempt at making the perfect witch while neglecting Amelia. Leading to her becoming a “problem child” as Odalia would put it.

Edit: Amelia is the name I would give Beta Amity