I'd be more worried about her eating the vacuum than the cardboard. Hope she feels okay. As far as I know, though, cardboard isn't too dangerous.

Sorry to hear about her destroying that stuff! We've had Adele for 2 years and she still isn't trustworthy while we're gone, we have to crate her. She just finds the most ridiculous things to get into. One time while we were gone and trying to let her have some freedom, she got a black ink cartridge (from a printer) and chewed it up all over my nice rug!! I was very upset....not only for the rug, but I was worried she might get sick from ingesting some ink. Luckily, most of it was on the rug and on her paws and she was fine.