I met this girl a few months back in college.After a while,we started talking,hanging out with others in our class... basically,became good friends.
I realized later that I actually like her a lot.we are totally comfortable with each other.
Lately I felt that she is also interested in me to some extent
(I think,you know how confusing they are! ).It was exciting and I was curious to know whether this could work out.

But that's when it went bad.
One of my friends saw her smoking near college.He now says it was most probably her(I think he's trying to play safe,by the way he is trustworthy)

Both of just turned 18,she had her first drink after her b'day.it didn't bother me at all.
But I just feel horrible that she smoked.I haven't done either!
Believe me,I am no saint and I know its weird that she is a lot more adventurous than I am.But I am sort of a 'decent' guy.I'm smart and fairly popular,we have a good gang of friends and have a lot of fun.she is great too,smart,fun,cute but I never imagined her smoking...

Yes,she can lead her life the way she wants to,and I have as good a sense of right and wrong as the next person.
I force myself not to like her,but its obviously impossible.Should I just calm down?
She'll always be my friend, but should I stop imagining her as something more than friends?

Cigarette or weed?
You haven't seen her smoke? Then she hasn't until you have, no matter how trustworthy someone else is.
I'm just not getting this anyway. You are hinging your feelings for her on a smoke? Please explain..

(I tried smoking when I was in high school, for about one pack's worth. I smoked pot for the first time when I was maybe 19, and still do on rare occasions 45 years later - for it's analgesic powers, LOL.)

If her smoking is a big deal then ask her about it, you are friends remember. If you can't handle smokers, and she is indeed a smoker then it goes no further than friends.

I don't see why if she smoked it would be a big deal. She's 18, she could legally smoke if she wanted. You haven't even see her smoke and if she doesn't smell like cigarettes or her breathe taste like them you have to reason to think she does. You shouldn't let something someone might have seen worry you so much, especially when it's something minuscule like smoking. I don't see how that would affect you being in a relationship with her or remaining her friend. You shouldn't place her on pedestal imagining her to be perfect, but you shouldn't give up on all hopes for a relationship though. She seems like a nice girl you're really interested in and you should give it a shot.