One of the first things should be securing the scene (e. g. warning flasher, warning panel) to make sure that it doesn´t get worse. You should only move the girl if it´s really neccessary.
You should preserve life and wait. Splints are usually removed by the paramedics to check the extend of the injuries. While you wait you should monitor the victim and offer to talk. Monitoring and taking care are pretty easy and really help the victim. It´s often neglected when handling an accident scene.