My 17 year sister was arrested a few days ago for DUI, open container, and possession of drug paraphernalia a few days ago. As soon as she got out of jail she didn't change her life at all. What do I do?

A month or two ago she told me she had tried heroin a few times but she was never going to do it again. I didn't tell my mom because I believed her and didn't want to betray her trust. Last week she was pulled over for driving drunk, and had an open beer in her car as well as a syringe.

She just recently got out of jail her and our mom tried to ground her. She started crying and saying she was really depressed and things of that nature. For some reason, god knows why, mom caved and let her go out. I talked to her on the phone a little bit ago and basically she's back up to her same old shit. I don't know exactly what she's doing but she sounded really fucked up and when I told her she needs to fucking stop doing that kind of shit or she is going to fuck up her life to the point of no return she just started saying things like "man you just don't understand" and "I'm getting straight A's in school what does it matter" and other bullshit. This has been going on and slowly escalating for about three years.

My mom told me she is basically just going to give up on her and not even pay for a lawyer so she can get charged with as many things as possible. Our family is not in the best financial shape as it is.

I love her deeply and this is incredibly painful for me. What's even worse is I'm over 300 miles away and in college right now. I have no idea what to do but at this point I'm convinced unless things drastically change my sister is going to end up as a junkie prostitute or something. Has anyone dealt with anything similar? I really need advice right now and I don't really have anyone to turn to.

*Edit: *As much as I fucking despise anyone who does this I feel the need to ask why the downvotes? This is a very serious problem and live and let live can't be the only advice to give.

I hate myself for asking this reddit cliche and in all likelihood it will probably backfire but I have to try as this means a lot to me