This depends entirely on how profitable you are and how much of a good person you want to be and can afford to be and if there’s any chance at all that one of your employees might be running his/her own scam.
Personally, I’d give her a refund, donate the item to charity or throw it out, then make a special effort to keep an eye on the employee.
This wouldn’t be the first time and employee was running a scam like this.
Unless this is stupidly profitable, I’d sell the place and get on with my life.