How do I support my sister who is experiencing “failure to launch?”

To preface, I love my younger sister (23f) very much. She has so many wonderful qualities, which is why it pains me to watch her struggle. I’m not quite sure how I can help, especially from afar.

Our childhood was turbulent and we didn’t receive consistent support or guidance from our parents who had their own struggles. With time and age, I have forgiven them and realized they were doing the best they could as young parents with heavy baggage. No hard feelings. But that took time. My sister is still early in the process of coming to terms with certain things that made our childhood difficult, which I understand.

Unfortunately, a lack of guidance has contributed to my younger sister’s “failure to launch.” Some of her issues began to surface while she was in high school, and I hoped that with time and encouragement (plus therapy) it might resolve in time for adulthood.

Now at 23, she still struggles to keep a job or even show up to work, maintain healthy relationships, or do “adult” things such as scheduling/attending appointments and taking her medication responsibly. She is frequently too depressed or anxious to work and will typically call in or no show at least once a week. She has little ambition as far as life goals, and even littler ambition to take responsibility for her own choices and seek proper treatment for her mental health.

I do feel that my parents have done their best in this phase of her life to show up for her, but they are genuinely maxed out on what they can provide both emotionally and financially. She shows symptoms of a mood disorder (perhaps BPD) and frequently acts impulsively and immaturely. This prevents her from keeping a job and having a stable income, as well as long term relationships. She drinks frequently and to excess. I’ve tried to express to her that adding alcohol to a concoction of SSRIs is unsafe, but she never listens. I am concerned for her wellbeing but I live in another state and I’m not sure how I can be more supportive. I try not to lecture her, but when I do offer advice from my past experiences, it falls on deaf ears and she continues to make the same choices.

How do I best support my younger sister who is having a difficult transition to adulthood? I want to see her thrive and mature. I try not to tell her what to do because I don’t want to push her away, but clearly my past approaches have not been effective.

Thank you for your help!