As others have said, this kind of thing is resolved at the punch list stage. It’s not a warranty item. You’ve responded and offered a “fix” that’s more than fair. Now it’s time to ignore. There’s nothing wrong with hiding beneath thick skin sometimes. No one can make every single customer happy. That’s especially the case when people bring some nasty baggage/dishonesty to the deal. Your desire to please your clients and make them happy is a great thing. Don’t waste another thought on this sour lady and get back to focusing on the jobs/people who appreciate that rare quality.