shrooms and lsd aren't going to hurt her by themselves. but if she's taking crap like coke, chances are she's not using a safe dealer.
the studies that show withdrawl symptoms from lab rats pump so much dope into them it's not even funny. no one would ever smoke that much. marijuana can be psychologically addicting, but so can the internet. the thing about dope is even if it had the potential to be addicting, it's presence in your body decreases so gradually it's like you're automatically weaned. the downside is you're still a little stupid two days later.
the problem isn't a physical addiciton but a mental one. marijuana is an escapist drug, you use it to get away from your problems, and that can be tough to kick. and in this case, she needs to kick it so she can deal with her problems.
millenium, i don't get how your personal experience with pills has anything to do with marijuana addiciton. for one thing, how can you single marijuana out among all the crap you were taking? and you mention yourself you were taking it to get "f|cked up," rather than feed a physical urge.
edit: realized much of the above has already been said in one form or another.