Tell your client to soak the nail in clear vinegar (not balsamic!) several times daily for a couple of weeks. She should understand that it may take several months for the stain to grow out. If, after three weeks, the issue is not growing out or the green discoloration is spreading, urge your client to visit a doctor.
The content is intended to augment, not replace, information provided by your clinician. It is not intended nor implied to be a substitute for professional medical advice. Reading this information does not create or replace a doctor-patient relationship or consultation. If required, please contact your doctor or other health care provider to assist you in interpreting any of this information, or in applying the information to your individual needs.