To me it looks like patches of bentgrass. The bent may have been affected by dry conditions or, if rainy--by disease. Bent has shallow roots and is more sensitive to disease. It is likely this happens every year when conditions are similar...but...now she thinks as a professional, you should be able fix it. Check for grubs.
Chances are--she will swear it never happened before. Fungicide or overseeding might help--probably not.
Once she is convinced that she has old, disease-prone varieties, and that overseeding will not help...sign her up for a Roundup, strip and resod job with modern top-quality varieties. Stadium green quality. Be sure to kill out all the undesirable grasses. Be sure the sod is disease resistant and contains no poa annua, weeds or bentgrass contamination.