I can't really say how to combat drug addiction, but the best way to change someone is to lead AND help by example. I know you don't want to hear it, but as long as she is having fun and everyone around her is doing it, she will not stop. ANY ADDICTION IS A BAD ADDICTION. I want to get that point across to you. If she is addicted, take her out of that state of addiction. If she is just having fun, there is nothing you can ask of her that you won't do yourself.
Note: Getting high or drunk and being addicted to getting high or drunk are two very different things. I doubt you're an addict, but your sister sounds like one. Take her out of the environment if you can, and ease off the drugs with her if you want her to stop.
That's my bit on habits. Hope you read it.
EDIT: And as for your relationship with your sister, I do applaud you good sir for sticking with her and trying to help. Most people would just ignore the problem if there is one, so you're on the right track. However, if you plan to destroy the only bonds between you (i.e. alcohol and weed), she probably will be none to pleased with you. If I were in your position, I would try to get to know my sister a little more. There has to be other things she likes besides mind-altering substances. Try to form a more 'stable' relationship that isn't based on material value.
And I know it isn't my place to tell you how to live but I hope any of this advice helps, even if you don't follow it. Goodluck!
Note: Getting high or drunk and being addicted to getting high or drunk are two very different things. I doubt you're an addict, but your sister sounds like one. Take her out of the environment if you can, and ease off the drugs with her if you want her to stop.
That's my bit on habits. Hope you read it.
EDIT: And as for your relationship with your sister, I do applaud you good sir for sticking with her and trying to help. Most people would just ignore the problem if there is one, so you're on the right track. However, if you plan to destroy the only bonds between you (i.e. alcohol and weed), she probably will be none to pleased with you. If I were in your position, I would try to get to know my sister a little more. There has to be other things she likes besides mind-altering substances. Try to form a more 'stable' relationship that isn't based on material value.
And I know it isn't my place to tell you how to live but I hope any of this advice helps, even if you don't follow it. Goodluck!