A head injury
which later presents with vomiting
must be viewed with caution. Vomiting could occur due to raised intracranial pressure. Headache is another manifestation which can be equally alarming.
You have mentioned she is not active as well. These are all warning signs which can signify an internal head injury.
Kindly get her reviewed with your Pediatrician
at the earliest and get a CT scan
of the head to rule out any internal injury.