Eddie
This is a classic, exceptions and over selling, Not that you over sold the product.
I was lucky to be one of the first 3M certified applicators, way back and we used to give certificates from 3M. problem was that people thought that it was the carpet price that got refunded if a stain would not come out, No, just the cost of the product. This misunderstanding lives on today in what people expect from these products. BTW these product have been in the past sold as having anti static properties.
Refund her money and put it down to experience. The problem goes away.
Respects & Good Luck
Ian