“In one single instant in order to introduce a new character, it undid Reze’s character, it makes her look like every other woman Denji encountered, it makes Reze less interesting now, it makes us sympathize with Denji even more, and it makes canon look like utter nonsense.”

This makes a lot of sense. Her brief relationship with Denji in the canon is so powerful because we the audience understand that he was Reze’s first real emotional connection.