Looks like Leukonychia striata, but I can't diagnose as I am not a medical doctor
Quoting from Wikipedia.
"Leukonychia striata, transverse leukonychia, or
Mees' lines are a whitening or discoloration of the nail in bands or "stria" that run parallel the
lunula (nail base). This is commonly caused by physical injury or disruption of the nail matrix. Common examples include excessive tapping of the nails, slamming a car door or extensive use of manicure.
[6] It may also occur in great toenails as a result of trauma from footwear. Alternatively, the condition can be caused by
heavy metal poisoning most commonly by
lead[7] or
arsenic.
[5] It can also be caused by
cirrhosis or
chemotherapy.
[8] The tendency toward leukonychia striata is sometimes inherited in an
autosomal dominant fashion. In other cases, it can be attributed to vigorous manicuring and trauma aforementioned, or to a wide variety of systemic illnesses. Serious infections known for high fevers,
measles,
malaria,
herpes, and
leprosy may also cause this condition. In many patients, there is no obvious cause, and the streaks resolve spontaneously.
[9] There is a similar condition called
Muehrcke's lines (apparent leukonychia) which differs from leukonychia in that the lines fade with digital compression and does not migrate with the growth of the nail.
[10]"
https://en.wikipedia.org/wiki/Leukonychia
I'd say ask your client to consult with her GP to get a definite diagnosis.