Dam I’m sorry for you I suggest for her to get a therapist and pour our her emotions and figure out a way to help herself . I understand what she’s going through I’ve been there but I wouldn’t have been here if it weren’t for my therapists I’m 19 I was 17 about to kms because nobody listened to me and I wasn’t getting my emotions. Validated. Going to therapy changed my life because when you speak you aren’t getting yelled at and that is healing . From what you said about your sister that shows that she is isolating herself and constantly thinking about killing herself and the only way for her to overcome it is to have someone by her side . If I were you try to like talk to her and like support her and find her a therapist once she goes to a therapist she will start to invest time in herself on whatever she has to do to overcome depression and what ever else she’s going through. That’s what happened to me and based of experiences that’s how I was so I mean by all means it’s important to get help ASAP and I’m lucky I’m even here I almost went over the edge thank god I didn’t but I’m a way better man now and I personally feel great and I plan on becoming a social worker or a therapist just because I gone through this and it made me a better man so i suggest you to help her out finding a therapist