F.H.
I'd agree that it could be car sickness. Had she eaten both times before she got in the car? Also I am not travel sick as long as I keep looking ahead. Does she read or color in the car?
Another idea would be the pepperoni on the pizza if she had any. Pepperoni can be the worst culprit for food poisoning.
If its neither of these then it may be a stomach bug or lastly could she be starting with a milk allergy? Was there anything else in the ice cream shes never had before?
Hope its just something simple and not a bug. Good luck