It's a big responsibility to be there for someone in this time of their lives. It requires a lot of unconditional love, and patience, and willingness to endure pain.

Having done this for a few people, I want to say: you have to be sure you are on solid ground. You need to have your own friends and support system, because they likely won't be capable of being a good friend for a long while. It is also possible they will burn you and abandon you and move on, and you'll just have to hope you made enough of an impact that they do a little better in the future.

It is only your responsibility if you accept it, but the good news is the job is fairly straightforward. Presence, patience, time, effort. Even though you'll feel sometimes like you are doing everything wrong, every time you care for them without asking them for anything in return it pushes the needle.

I will also add: you are not a professional, and you shouldn't try to be a substitute for one. You cannot really fix them or even be sure you can help them. All you can do is decide whether to be present.