How long ago it happen?
Do you see swelling?
How is she acting right now?
I know she (and you) are very scared.Hiding is normal from fright.
If it swells up or she has a seizure, becomes unconcious, vomits, cant eat or her eyes dart back and forth she will need to be seen.
Give her some time to get over her fright (half hour) ad offer tuna water or milk to drink. Canned food or tuna to eat.
Just watch her the rest of the day because when and if the brain swels she can show symptoms. If she acts normal she should be fine.
Please let me know how she is later. I hope all will be well.
Sincerest best wishes,