Jumpy

Hello everyone. I read through a lot of the old threads, but didn't find any that addressed my situation, and I'm very concerned.

My girlfriend is not really a user at all, but on occasion, she has smoked with me. Over the past 90 days (which I've read is the time period that a test measures), she has smoked three times, each about a month apart, with the last incident being three weeks ago.

Today she received a random hair test. How concerned should we be?

And is there anything she should be doing now? (As in, if she tests positive, what can we expect? Follow up tests?)

Thanks for any help you can provide.