I found this on-line:
Canine's Corner - Artifical Sweetners Can Be Harmful To Your Dog
It does state that if you think your dog has eaten
xylitol, even a small amount, to contact your vet immediatly. If you don't think the ice cream contained this product, just watch to make sure the Yorkie is okay.
Please let us know how she's doing. I would also recommend keeping all people food away from Lily. It's the best treat you can give her 