I don't know what to do

I'm iving with my sister abroad.

She was recently diagnosed with adhd and was having really serious drinking issues. She used to try and drink her problems away before she was diagnosed with adhd. She did tried to kill herself once by alcohol overdose herself.

After getting medication for adhd, she said she will stop drinking. She said she went to AA everyweek and I didn't see her taking alcohol anymore.

Last week, I was away for a few days and found a zero alcohol beer can in her room. She did drank some sparkling wine without alcohol over the holiday too.

I went out to my room just now and smell a really strong smell from her room. I'm can't be 100% sure if that's the tabacco smell or not but it smells like it.

I did tried to talk to her about it and asked her how she's doing. But we need to work in the day and in the evening she would usually stay in her room.

We don't get along too well most of the time because sometimes the things that she said can be a bit hurtful. For example, when I told her that I enjoyed watching comedy she would said I had a sad life and that's the reason why I loved watching comedy to cheer myself up. I may be a bit oversensitive but I really don't like it when she said that.

Even that's the case, I don't want to lose her too. She's my only siblings and I have the responsibility to take good care of her.

I don't know what I can do. I don't want her to try and kill herself by overdosing anything. When I smell the tabacco like smell from her room, the moment when I found her overdosing herself comes to my mind. I can see her getting incubated in the hospital when the doctor was trying to save her. I can't seems to get rid of the picture of that out of my head.

It has been few months since I often had nightmare about that day when I found her overdosing herself.

I'm really scared and I don't know what to do.