Unless the car park is designated as a public place under the relevant road traffic laws, the Police would not get involved.
How do you know she reported you to the Police? Does she know you, i.e. your name and address? Have the Police contacted you?
You do not say how much, if any, damage you caused to the moped and whether or not you inspected it in company with its owner? How do you know that "the young lady" as you call her is its owner?
No one here will be able to give you a satisfacory answer unless you provide more details, I'm afraid.