Chemotherapy Permanent Hair Loss

My mom was on Taxotere for serveral years, the first year she had 54 treatments and now it has been 5 years since this long journey began and she is Cancer Free. She has been off of the chemo for well over a year and her hair is coming back, but it is so thin it looks to be the hair of a 80 year old man and she is only 52. Her chemo office told her she needs to see a specalist because they aren't sure why her hair isn't growing back.