How can I respectfully stop a pagan from littering?

[FrodosPet]

I have a dear pagan friend who professes to love the Earth and hate the big polluting corporations.

But she is a smoker who thinks nothing of throwing cigarette butts, cellophane, even food wrappers out the window of a moving car, excusing it by saying everybody does it and it helps create litter cleaning jobs.

I am doing my best to be as non-patriarchal as I can be. I desperately try not to either tell women what to do, or to even make any kind of suggestion lest it be perceived as telling someone what to do.

But still, littering bothers me. Should I say something any stronger than I already have, or should I just accept that saying something, no matter how benevolent I think it may be, would only be met with negativity?