I think talking to her would be a good idea, but you'll have to use reverse psychology.

Do like Karen suggested and say you're planning on saving your $$ for college and ask her opinion on how she'd do it if it were her. Ask if she can help you open a bank acount like a CD where you CAN'T take the money out.

I think that if she saw your $$ was going to a savings for your future, she'd have a harder time demanding it each time she wants cigarettes.