Your client may have one of several conditions. One possible condition is superficial white onychomycosis, a superficial infection of the top layers of protein in the nail plate. The infection does not usually cause the nail to separate off the nail bed as is the case in the more common subungual onychomycosis, but the infection may eventually damage enough protein so that by the time the nail has grown to the free edge it becomes brittle and fractures. This sort of peeling of the nail plate in layers is referred to as “onychoschizia.” Treatment consists of using topical Clotrimazole solution applied twice daily with a toothbrush. No prescription is needed.
Another possibility would be some variant of psoriasis, lichen planus, or other skin condition that causes pitting. These occasionally look like blisters and the nails can appear hard until the nail grows out and then characteristic brittleness appears.
A third possibility would be a variant of traumatic leukonychia. A slight irregularity in the decomposition of nail protein as it forms can lead to the appearance of small partial transverse bands that may occasionally look like blisters. Most commonly this is caused by picking the proximal nail fold or overzealous manipulation with manicure tools. — MacDougall