I literally say it in the post. Magic Scissors. The only factor remaining is Raven at that point and dealing with her is complete luck, in which I'd have a better chance against her than with. I'm not really relying on Star in any significant capacity, just the ability to hide in another world.
Also Star isn't retarded, she makes mistakes, there is a difference. Characters who succeed at everything they do, or only fail because of things out of their control are boring and stupid.