The powers of the notebook in and of themselves are somewhat manipulative. I don't think Addie was using it with bad intentions though. I think she genuinely really liked Melanie and wanted to get to know her better and felt like she needed a supernatural or magical way to get Melanie to notice her. But as another commenter suggested, perhaps Melanie is the magical one, really liked Addie all along, and the notebook never really did anything. To be honest, I have not fleshed this story out that far haha.

The stuff that happened with Melanie's family had been happening for a long time before Addie ever wrote her name in the notebook. Addie was just the first person she ever told about it. Now was it because Addie had gained Melanie's trust artificially due to the notebook? That might be one of the main conflicts of this story!