As Auntie lacks the biological urge to reproduce she can't speak from experience - though she was once stepmother to two media brats with a mummy and daddy who stuck enough coke up their noses to fall just short of needing nasal reconstruction. While the brats could roll a better joint than Auntie, they had no interest in partaking themselves and treated their parents with mild scorn.
Unless you've pawned her iPod to pay for crack, the 'Do as I say, not as I do' approach invariably backfires, and if you decide on full disclosure she'll probably think 'Mum's hardly Peter Doherty and gets through the day without being arrested, so drugs can't be all bad.' There's a fine line between no-holds-barred confession and lying, but Auntie has some prepared scripts that might help you out.
There's the Hazel Blears 'I had one or two puffs but it didn't work' approach; Jacqui Smith's 'I am not proud about it, I did the wrong thing'; Oliver Letwin's 'I was tricked into it by friends who put dope in my pipe'; or even the George Bush manoeuvre: 'When I was young and irresponsible I was young and irresponsible.'
Alternatively, you could contextualise drug use with larger social issues, such as the brutal trade involved in cocaine or the CIA's role in funnelling drug money into weapons and war. Auntie also knows a couple of brain-addled ex-friends who would be happy to talk gibberish to your daughter for a week in exchange for a few wraps of coke - enough to put anyone off drugs for life.
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