20 days clean....

Everyone, I know there are tons of these threads and I am adding another just to get some reassurance..
My wife has a drug test tuesday 11/30.. she has been clean since 11/11 (last time she took a hit was 11/10) so she will be taking the test on the 20th day of being clean... She is a daily heavy smoker...
She just now drank 3 pints of water after taking a piss and then just went back and took a home drug test for THC.. there is a VERY VERY faint line on the THC marker (but really you have to REALLY look for it)

what do y'all think? Should she do anything or is she going to be clean? is there anything she should do in the next day and a half to make for better chances?

TIA!

more info on her...
5 foot 9
Slow Metabolism,
Low Body Fat
140lbs

No one will be able to tell for sure. Check out the dilution sticky, make sure she follows it. If she's been exercising, stop.