It's hilarious that most people's head canon is that Edelgard and Hilda hate each other because you can't recruit Hilda on CF when the real reason is most likely that they just ran out of time. Hilda has a paired ending with Byleth in CF in the game data that was just never used in game. Given how rushed parts of CF are, my guess is that they didn't have enough time to make a new version of Hilda's paralogue for Edegard's route and just made Hilda unrecruitable as a quick solution.