I agree with Karen that you are a good friend. I am guessing that you are in school. If that is the case, you can talk to a teacher, coach or counselor. Pick someone you trust, if possible choose someone who knows you & your friend both. It is normal to be upset again about a loss after some time, but what she is doing is very, very dangerous. She needs to find a safer way to feel better about things, but that is easier said than done. An adult who knows both of you should know how to talk to her & get her connected with people who can help her with all those sad feelings.
You could also try encouraging her to talk to her mom. Her mom knows what it feels like to miss her dad & they can try to figure things out together. Sometimes young people feel like they don't want to "upset" or "bother" their living parent with their problems since they know mom/dad are probably dealing with their own sadness (sometimes not very well) but the reality is that even if their living parent is sad, usually they are the best able to help their child process their feelings about the loss. And helping others, especially one's own child, tends to make the adults feel BETTER about themselves, NOT worse. I know it doesn't seem like that's possible, but it's true. Parents like helping their children. They feel good about doing that. If they are really sad & get to help their child deal with grief, they will feel better. So that really is the best option.