Hi and Welcome!!! This is a great place for parents because we really understand and have been there done that. No judgements either!!
My first question is do you really know what adderal is? It is a stimulant, a type of speed. It is addictive. Many users use meth if they cannot get adderal, or if they aren't getting as much of a high off of adderal anymore. It is very very dangerous to crush and snort it or to crush it and heat and inject it because the fillers that let it take pill form are not meant to be in your lungs/bloodstream.
Do you REALLY want someone who is stoned to be driving a car? Regardless of if they are on uppers, downers, or something else, they do NOT have safe judgement and it is illegal for them to be driving. Your daughter should NOT, under any circumstances, be allowed to drive. Take the car away - make sure it is undrivable by taking parts out of it because I would almost guarantee that she has a couple of spare sets of keys around the house, if not on her friends' keyrings in case you take hers and find the spares in the house. It is pretty easy to remove a spark plug wire or two - ask at any auto parts place and someone can help you learn to remove and replace a part or two easily so that it will not run.
Or else sell the car. Do NOT put the car in her name, either.
You are going to have to crack down hard to convince her that she wants to come clean. Mostly she doesn't and unless she hits bottom (probably MUCH lower than you have ANY idea) she is not going to stop getting high. She is likely already addicted to the point she is using every day. As soon as it is hard to get high with the adderal or it is too expensive, someone will let her try meth. Meth is cheaper and you get a LOT higher from it so it is very attractive to those who snort stimulants like adderal.
TODAY you need to make sure you have a strong deadbolt on your bedroom door and learn to use it religiously. The key to it needs to be around your neck or in a tight front pocket - somewhere you will KNOW if she takes it off you. Put ALL medications except her birth control, if she is on it, in there. She can get high off of many cold medications, esp those with DM in them. DM stands for dextromethorphan and is VERY popular for getting high - and VERY dangerous. In normal doses it is safe, but addicts drink bottles of it at once, which can kill them.
If she won't see a doctor or counselor (therapist), she doesn't need to drive. If she is getting high no one wants to be on the road with her and NO ONE is SAFE when she is behind the wheel. I am sorry to be so blunt, but it is true. Adderal does NOT change seritonin. SSRI's are the medications that affect seritonin and are used to treat depression and anxiety. Prozac, zoloft, etc... are SSRIs for depression. Adderal is a stimulant used for ADHD and widely abused to get high.
Adderal is NOT making her less anxious or depressed. It makes her high, twitchy, can cause incredibly anxiety and feelings of paranoia, among other things. It makes people unable to sit still, to stop moving, to be calm. If she has told you it helps her anxiety and depression she is lying to you.
PLEASE insist she see the doctor, and take the keys and disable the car until she can prove she is clean. You have to be very very strong because this is a very dangerous addiction. It is very likely she is already addicted, and if it has been going on for long she likely has tried meth and may be using meth instead of the adderal she admits. From the addicts I have known, they are not likely to admit all of what they are doing. If they admit pot, they have moved past it. As she has admitted adderal, she is likely using a LOT more.
This is illegal. If she won't get help on her own, you may have to get the police to help you. Or the school. If she is getting drugs at school you owe it to her and to the other kids at school to tell the principal about it and to get her and all her friends tested. She may get expelled but she will be able to finish her degree or get her GED later.
This is very, VERY likely to KILL HER. If she drives she is far more likely to kill herself, anyone with her, and anyone else on the road with her or the sidewalks near her. IF it can be proven that you knew she was getting high and continued to let her drive some states can hold YOU financially responsible.
You must come down HARD on this. IF you know her friends' parents, or can find their home numbers, telling them that their children may be getting high with her will do a couple of things. It lets them know they need to look closely to see if their child is in trouble. It lets them know that their child may not be safe to drive, and may be at a huge risk if they drive. It also will likely result in them telling their kids to not be around your daughter - cutting off various sources of drugs for your daughter!!
Personally, I would tell just to try to cut off those avenues of drugs.
IF you let this slide you are setting your child up for a very painful, sad, sick life. One that is likely to be far shorter than it has to be.
Please attend NarcAnon meetings and/or Al anon meetings. They will give you a LOT of much needed support. The 12 steps are the same basically for each group, though Narc Anon may feel like a better fit. Give it 7 meetings in 1-2 weeks before you decide it isn't for you, and try meetings in different places/times until you find one that feels right for you.
Many hugs, this isn't easy and you are not alone.
