Vixen
Penultimate Amazing
tested negative for drugs = didn't have drugs in system
what were her minor living expenses? did she pay tuition and buy books? did she eat in restaurants and drink at bars and clubs? did she buy train tickets? did she buy clothes?
you have no idea what the withdrawals were and what she spent money on.
Not necessarily: Cocaine itself metabolizes faster than most drugs of abuse and cannot be measured. Therefore, the body of the user will determine how accurate testing will be. When the use has been a long-term, consistent habit, the blood, urine and other forms of testing will strongly tend to be accurate. However, depending on the size of the user and the history of their use, it is possible for tests to fail.
Those samples taken too early after use may measure a false negative.
http://www.thegooddrugsguide.com/crack-cocaine/drugtests.htm