How worried I would be depends a lot on how much fabric and foam is unaccounted for. I'm guessing the couch did not have covers on the cushions? If you think she was mostly shredding and not eating, I'd just keep an eye on her. If there's a lot of foam and/or fabric missing, I'd be a bit more concerned.
Oh, and by the way... YIKES!!! Will your kids be paying for the damage out of their own pocket money?