Yay! Make sure you get a good cover on it now. Kitties are smart and can sometimes learn how to pull the vents up. . .now that she knows how much fun it is in there!
I had a cat get stuck in my vent system. Make sure you watch her for coughing. I had to take mine to the ER vet because all of the dust and stuff that was in the vent system got in his lungs and he ended having trouble breathing. We had to put him on antibiotics and an inhaler to clear the junk out of his lungs.
I'm so happy to hear that your new fur baby is safe. I'd check all your vents and make double sure she can't get in them. Good luck with your new baby.