In a child I would thing 12 - 24 hours would be the normal time frame for symptoms. At the same time with such a busy day you can expect her to be tired etc today anyways and throwing up from getting too much sun and getting over tired is not unheard of either - I have an adult daughter that to this day needs to keep the balance of both in check.

In the grand scheme of things even though there is a best practice for food handling many foods are eaten after sitting out more than the recommended 2 hours. One thing in her favour is that the car would have been so hot that it would be like the food was still in the oven and a lot of bacteria doesn't start to form till the foods cool down to room temperature - hence the two hour warning. The heat of the car might actually have prevented food poisoning although a reminder to never do it again is for sure in order.