What can I do for the sake of us both?

my friend began smoking pot about a year ago, and from there began smoking cigarettes. at the beginning, smoking (pot) was something that kind of helped us bond. so we both did it a fair amount - probably about once or twice a weekend. and i would take a pull of a cigarette every once in a while, but after smoking became a "habit" for us, i started to have second thoughts about it. and because singing is a hobby of mine, i began to feel some remorse. so i started to take it easy and take it into moderation, but this wasn't the case for my friend. she still smoked (pot) constantly, making it into a real habit. cigarettes, too. she is addicted to smoking, more mentally than physically, but no matter how concerned i get and no matter how hard i try to explain to her how she needs to moderate herself, she says that she doesn't care or i don't understand. is there any way i can help her before she turns into a complete burnout?