http://www.wrigley.com/wrigley/products/brand.htm
It looks like Orbit does contain Zylitol... but I think it's promising that she threw up the gum and she's acting okay right now. Still, I would give your er vet a quick call and see what they say - I imagine they'll tell you just to watch her, but at least you'll have a little peace of mind.
Hope your baby is ok!
P.S. If it was Orbit White, it does NOT contain Zylitol.