Dude, you're too young to be *doing* drugs yourself, let alone teaching her about it. Even if you yourself are intelligent, rational, sensibile and careful, your brain is still developing. When I say that, I don't mean you shouldn't do drugs because you don't have the maturity or the intelligence or that you're not emotionally stable enough or whatever - it's completely possible that you very well might be completely ready mentally in every respect to be able to handle drugs and what they do to you. However, during adolescence, when the brain is still developing, drugs can harm you in ways they would not harm an adult.
I don't know if you're smart enough to grasp this concept properly so I'm really trying to simplify it for you so you get it because it is important that you know this if you're already using drugs - drugs are not good for the brain. Some drugs are particularly bad for the brain in that they can actually alter the brains structure and in extreme cases kill brain cells. We call any damage to the brain "neurotoxicity"> Neurotoxicity is very, very bad. Damage to your organs is another effect of some drugs, obviously, but unless we're taking practically letahl doses of certain drugs then it's not one that we need to be *too* concerned about, because any damage will not manifest itself until a few decades down the line. Neurotoxicity is not like that. If you use drugs at your age it's honestly completely & entirely possible for your brain to sustain structural damage literally whilst you take that drug and for the cumulative effect to begin manifesting in your behaviour in under six months.
By "brain damage" I am not talking about dramatic differences like losing the power of speech and drooling all over yourself all day struggling to feed yourself or something, I'm talking about subtle differences in your personality, behaviour and emotions. It could manifest itself as you getting slightly slower over a long period of time so that you don't notice the effects, until all of a sudden you're looking back at you when yourself and thinking about how you used to be so much smarter, learn faster, read faster, was wittier in conversation. Have you not met any "burnouts" yet in your drug use? There are plenty of them around, and I'd wager you'd be shocked at how they turned out if you could compare them to how they were ten years previously - I've seen it happen to people myself. You could slowly lose your motivation and drive, sleeping more, procrastinating more, until you find that you don't do *anything* with your life because all your get up & go has got up and gone, until you're looking back and thinking about how motivated, energetic and productive you used to be. You could start noticing your mood has started to dip a little bit and you write it off as just having a bad week or month, and it gets worse & worse & worse until all the joy has been drained out of your life, you find that you enjoy NOTHING, your internal monologue has become a permanent stream of self-criticism, you feel extremely sad and empty and contemplate suicide, and you look back on how happy and healthy you used to be. You could start finding yourself a little more uneasy in social situations, just a tad, and then you find yourself with your eyes down on the ground a lot more than you used to when you're walking along, when you're heading to a party or just a gathering you find yourself getting really nervous and edgy, and before you know it you're an anxious mess, looking back at how confident you used to be.
These are just a few examples of the *kind* of damage I'm talking about when I mention neurotoxicity - it won't start dramatically, it'll be so subtle you hardly even notice it till there's a real problem. All of this is a very, very real possibility when you start using drugs at your age. You might wonder why you can't safely use drugs but a 19 year old can, and thats simply because drugs have different impacts on the developing brain. It is a
well established fact and is widely accepted among scientists that even weed, just weed, has a neurotoxic effect on the brain when taken in adolescence, something that does not happen in the brains of adults. A quick search here on Bluelight will show countless threads - asking for help, asking for guidance even some just warning people - made by people who very much regret their adolescent drug use, as they are now mentally ill or they even just feel very "changed" - slower, or anxious, or depressed, totally lacking in motivation and energy etc.
I hope that you have actually read this. I don't know how smart you are, so I have no idea if you've fully grasped what I'm trying to tell you or if it's gone over your head. I guess in terms of your sister it depends on what exactly you're planning on telling her?