Yeah I went and read up on it. Emma Frost basically told Jubilee she could destroy matter on a subatomic level if she wanted to, meaning she'd be insanely powerful. Problem is Jubilee lost her mental control once or something and killed people, so she was really against letting herself get any stronger.
Of course now she's a vampire (bitten by the son of Dracula, of all things), so it doesn't matter. Boooooooooooooring.