YOU need to control this, don't mention delayed refund, simply ask her to return the car or you go collect it if local to you, then once you have keys and car, get it looked at first, before issuing the refund ....................
If she get's all aggy once you have the Keys and Car just tell her that there will be no delays but it is your "company policy" to inspect the Car at your workshops and only then will you issue a bank transfer or she can collect the cash and sign for receipt of it !!
HTH,