I would keep a close eye on her, maybe wake her up again later to make sure she's ok. Generally if one gets a concussion, they say to wake the person up every so often that first night to make sure they can come to conciousness. Did she black out when she was hit? I would say if she didn't have a headache when you woke her up, just keep an eye on her. If you wake her up again and the headache's back, take her to the ER tonight.