Same thing happened to my little brother.
He still lives at home (age 19, extreme slacker, has part time job, no school) with my parents. They found a large chronic nugget along with two glass pipes in his laundry.
Of course, one of those glass pipes might have been his older brother's, and he might have also gotten the nugget from his older brother as well -- but probably not, because we all know drugs are bad.
Anyhow, they pulled the same trick. Sat him down, asked if it was his, and gave it back to him. (BTW, for any of you wondering, he didn't turn his older brother in). Then he got the same lecture I got when I left the house.
Throughout our lives, my little brother and I worked under the assumption that my parents were as pure as driven snow. They claimed to have never touched drugs, only drank to excess once, virgins when they were married, etc., etc., etc. When I left the house, my father told me the truth:
My mother had done every drug known to man short of MDMA (slightly ahead of her time). She had fairly high connections, so she got to play with anything she liked at a fairly reasonable price.
My father dealt drugs through college. LSD was his specialty, but he got busted on intent charges for marijuana, plea bargained down to a misdemeanor possession w/probation.
It was an interesting lecture when I got it (right before I moved out and right after having finally admitted to having "tried" ecstacy ["tried once" being slang for "just coming off a 2 month binge because it was losing the magic"]) and probably a little more interesting for my little brother, who got it while he had a nugget burning a hole through his hand.
For what it's worth, although my father and I sometimes discuss drugs (he was interested in how MDMA worked versus LSD in particular) and I use a "harm reduction" stance for all the knowledge I have, it's *never* discussed that I still to this day use drugs.
I compare it to an episode of "Will and Grace" I saw once, where one of Will's lovers couldn't tell his dad that he was gay. As a result, his family *knew*, but they wouldn't talk about it.
I'm not gay, I just use drugs. Same dealie though.
I guess what I'm getting at:
1) It's highly likely that your mother has smoked marijuana before. Very few people who lived through her era can make the claim that they haven't.
2) While your mother may not be cool with it, she probably respects your privacy enough to not bring it up with you.
3) Until you know where she stands on "harder drugs" (I'm not sure what exactly you use if you *don't* use weed), I wouldn't bring up your other use. Marijuana's almost accepted as "harmless" where as MDMA is being demonized as the next crack cocaine and oxycodone is super-synthetic heroin for the new generation. Try watching one of those news specials on drug use with her instead of going out one night. Feel her out on this one.
My family operates on a "don't ask, don't tell" sort of basis. I feel bad about it, but I *can't* expect my parents to be ok with my continued use.
However, you could get lucky: my best friend told his mother that he does LSD on a regular basis without a problem. She's aware that he does it, and apparently is cool with it if he feels it helps him.
You could get *real* lucky -- she might have better weed than your friends.
