If this were me, I'd fix it at her expense. I would not be satisfied letting a customer try to fix it. Chances are high they will botch it and chances are even higher, like 100%, that they will tell everyone who built that nice table with the ugly finish.
If she refuses to pay you to fix it I would walk away w/o offering any advise on how she should go about it. That's just a no win option.
Also, going forward it would be a good idea to look for higher quality finishing products. As you now know, Polyshades isn't all that durable.
John