Yes, most likely that is exactly what is going on in a situation like hers. Costochondritis occurs in both adults and kids but more in children because of all the physical activity they have.
Give her some ibuprofen and that will usually relieve the pain/pressure for up to 4-6 hours and you may continue that medicine every 6 hours or so while she is awake for the next couple of days. As long as she is breathing ok then you need not worry.
Please let me know if you have any questions.
Thank You Dr. Clark, I appreciate the help.