If you know it's stupid of her, and bullshi*, then why should you be reluctant to call a spade a spade?
On the minuscule chance that she's telling the truth about them being a "friend's," I'd say she deserves your lack of trust just due to her display of lack of judgment for even possessing such an item, for a "friend." Next it will be hard drug paraphernalia, and do you think the cops will listen if she gets caught and tells them the stuff is her "friend's?" She may as well learn early there are consequences for even being in a position where it LOOKS like she's guilty.
Don't base your response on what may or may not be "true." Base your response on WHAT IS. SHE WAS CAUGHT IN POSSESSION OF CIGARETTES.