How Long Do Drugs Stay In Hair?

I disagree with the above answer. The hair folicle contains the history of a person's drug use. A tester will usually test the 1" to 2" hair closest to the scalp in order to get a current time period reading. Most people believe the test is done to the end of the hair but it is actually done at the beginning of the scalp to get an accurate present-day reading.

No, it doesn't it takes at least a week or so for it to show up long after the effects of it are gone.

It depends on how much drug she done, and how long her hair is?
I would say, get her hair cut...
To be on the safe side!

That would depend on how long your hair is. If you keep your hair short, then it would be grown out and cut out from the testing. If your hair is longer, then yes it will show up in the test. Everything you ingest is evident in your hair for as long as you have hair or until you cut it out. Your hair grows about 1/4 inch per month.

They can see approximately fifteen years worth of drug use testing that way.

90 days

The drugs eventually show up in your body fluids and hair in one form or another. The hair test can detect weed and drugs for about 90 days and after that these are gone.

Some last the lifetime of the hair, some 90 days, some 30 days, and some only a few days. en.wikipedia.org