He owes her to come out and see if the problem is related to the first problem free of charge.
She owes him labor and parts for any additional work he does unrelated to the first job.
I agree. he was paid to fix the issue. he should at least come by to check if its his error. if not, he can offer to fix it for an additional fee for his time and labor. that's what I consider service. a good reputation is very valuable.
I had a closet guy mess me up by not telling me something important about the layout we worked out for my closets, and caused me additional financial expenses to fix it. I didn't demand my money back, but he's off my list in the future. I refuse to give such people my precious money and business.