That’s my biggest fear that 10/20/30 years down the line it’s not just the occasional bit of puff.
Don't worry about it, it's her life and if she wants to smoke weed she will do, you can only guide her.
Those who I went to school with none of the stoners have turned out successful (by any stretch of the imagination).
None of the "stoners" isn't the same as none of the "people who smoked weed", lots and lots of people do it a lot more discreetly than the visible stoners. Many people carry on smoking through life and lead very normal and successful lives/careers.
I'm 40 and use cannabis daily apart from breaks every few months for a couple of weeks.
This has largely been my pattern since I was your daughters age (although I have sometimes not done so regularly), I currently work in finance in a managerial roll, earn a very good salary, have a happy family and generally lead a full and varied life.
I'm not the exception either, the way I consume cannabis is very much the rule for people above college age. Obviously it is more visible when people are doing it on the street and these people are generally not how you might wish your daughter to grow up but that's just the visible image and the image the media might like to portray. The majority of over 25 year old smokers do it behind closed doors, occasionally in the park or whatever or even they do it out in the street but you would never in a million years guess that they were as they will make sure there isn't the smell etc.
Basically, don't worry about her so much. She shouldn't be smoking at that age as it isn't good for her developing brain but she's going to do it and she will definitely get some more in 5 minutes if she wants. There are some useful ideas above about giving CDB supplements as this helps to counteract the THC, basically the best you can do is educate yourself about Cannabis and then educate your daughter.