2 oz is the minimum sample they will accept so make sure you fill the bottle completely. Smoking only once, you will be clean in 2-3 days. Its if you smoke more times within that 2-3 days that the metabolites are compounded in your body and it will take longer to get rid of.

If your girlfriend only smoked once 2 weeks ago, she will most likely be clean, but if it were me I'd just spend $20 on some QuickFix and leave no question as to whether or not you will pass, especially if its important that you get the job.

Also, the only time you might get patted down is possibly for a DOT test or a test associated with probation, parole, etc. Also, if the job you are getting is associated with the DOT, you can substitute to get the job, but they just started doing supervised randoms, so substitution will not be possible once you get the job if you get popped with a random. Good luck!