it seems to be a case of gastroenteritis
in first look rather than related to any head injury
, but "projectile" vomiting puts some doubts. though viral diarrhoea
may also sometimes have vomiting that may seem to be projectile. you should get her evaluated once for her complaint to get her examined physically by a pediatrician
. meanwhile give her home made fluids and ORS (oral rehydration solution) to keep her replenished.