buyer/seller integrity question

Caveat emptor
I sold a 08 Chrysler Pacifica to a young lady last summer. It had been my daily for the past several years and it was time to upgrade. I wasn't going to pay to fix the A/C.
The girl bought the car cheap. In fact, all I really did was recoup the amount I had in it for a recent water pump/timing belt job and a set of tires.
She drove it around a couple thousand miles and water tube leaked and I guess she over heated it.
She and her dad were at my door wanting her money back.
I told her no. I had no idea what she had done to the car after it left my control. I had no way of knowing that a water tube would leak, and why didn't she get it fixed instead of driving it with a leak.
In the end, I, like you conducted a sale in good faith. The car was sold as is where is. I'm sure you gave your buyer the opportunity to drive or inspect the car before they bought it. If they didn't, then buyer beware.