Re: If a headache comes on after hitting the head...
Of course it's your call, and most garden variety knocks on the head do not need a rush to the hospital...It's good that you have your eye on her, and by now it is likely a moot subject..but I still like to reply.
The main reason I would suggest a doctor to check head injury fist thing, is that with the little bit of information, I had to. We do have poster's who seek help for some scary things sometimes, and it is better to give the right suggestions.
The main thing the ER would offer that you don't have at home would be the imaging equipment (MRI/CATscan) to find injury, to assess the severity and to decide on a proper treatment.
There are some very delicate parts of the skull that could easily fracture if hit just right, there could be swelling, nerve damage, a bleed...you name it.
I am glad that your wife is feeling well, and she is lucky to have you watching out for you...I wish you well.