She’s an adult and still has the capacity to make her life decisions. She has decided that this is how she wishes to live her life and there isn’t much you can do from what you already tried. She may eventually hit rock bottom and then try to crawl back out of that terrible hole. Hopefully she’ll not take anyone else with her or hurt anyone else. Unfortunately in life some people just make bad choices for some reason that they may or may not recover from. You’re a good soul with a caring family and you’ve all tried your best short of criminally disabling her vehicle to get her to see the light without success.
You might consider contacting a therapist for you and/or extended family so you can get some insight into her mindset and self support in this difficult time. I am sorry for the situation you’re dealing with.