It could be an insect bite as said by you, could be an infection or allergy
. It is the rate of progression that you need to be worried. Usually it will subside in one or two days. If it is increasing then you need to show it to your gp. You can try soothing lotions like calamine
Don't worry she will be fine.
Dr. Balaji Chinnasami MD
Assistant professor - Pediatrics