Portrait
Have you considered going to Al-Anon or Nar-Anon for yourself? These are groups for people who are affected by the drinking or drug use of a loved one, respectively. They may help to give you some perspective on how you can support your daughter while protecting your own physical and mental health and without enabling her.
Also, might it be possible that she DOES have ADHD but it was simply never identified? This is a very common phenomenon with girls and women, especially because most women who have ADHD have primarily inattentive subtype. They don't have the "bouncing off the walls", "driven by a motor" behaviour that you tend to see with primarily hyperactive/impulsive ADHD. Instead, a lot of the hyperactivity can be in their minds and can manifest as overthinking and over analyzing things, and can often be misdiagnosed as anxiety and/or depression. (I speak as a woman with suspected, although not officially diagnosed, ADHD that was identified by my stepdaughter when I was in my 30s. She has female friends who have been diagnosed with ADHD and saw many similarities between me and them.)
You might like to look into the lived experiences of people with ADHD (ADHD Chatter podcast, LifeActuator, ADHDLove, and Holderness Family Laughs, all on YouTube, would be good places to start). It's possible that you may find that many of the things they describe are similar to behaviours you've noticed in your daughter. One experience that's almost universal in ADHD is rejection sensitive dysphoria, or RSD, a very strong negative reaction to any form of rejection (including things such as perceived rejection and criticism). This can make for more difficult relationship experiences. Emotional dysregulation is also a feature of ADHD, and people who have ADHD may potentially be at a higher risk for substance use disorders, given that substances can increase dopamine, and people who have ADHD have dopamine dysregulation issues.