Most probably, it is Alopecia Areata. Please see the dermatologist as Alopecia is autoimmune in which body's immune system goes blind against its own hairs and attacks them. But alopecia areata is curable and need not to worry about it much.
Regards, Dr Dhananjay Chavan Dermatologist
There can be few reasons,if she is taking chemotherapy,if yes,then this is one of the side effects of chemo,this happenes but they grow back,so no need to be worry about that. Harmonal problems or even some infection also.
Their immune system may be attacking their hair follicles. That is alopecia.
Could be Alopecia...or is she on chemotherapy?