ACCIDENT? Did I miss something?
In some areas the Police are required to issue a ticket at all accidents where there may be injuries.
They often use the “fail to control vehicle” section.
Often times the ticket is issued (in my state NC) to get you to prove insurance coverage at the time of the accident. (I don’t know why)
Also the other vehicle was parked. Your son was moving and except for blinding him with the lights, he would have definitely been at fault.
I still say Fight it.
So bring proof of insurance so you have it with you if they ask for it. Explain the situation as I suggested, except don’t say it was a good thing she had her lights on, instead emphasize they blinded him, and were the real cause of the accident.