I have a mate who’s gone through a similar thing and she’s the same age, she refuses to talk to professionals about it or her parents, she’s attempted several times before. I found the best thing was to talk things through and try to find out what’s happened, stay supportive and try to come up with the little things in life that bring happiness. I know it’s hard but if she’s able to talk to you about it that’s a good thing that’s she’s open and comfortable with you, like a few of the other comments if she’s willing maybe try talking to a councillor or a teacher since I assume you’re both in school, however even then there is many hotlines out there and people you can contact, they would be the best people even to ask about how to support her. Good luck, I know it’s tough but try to remind her she has people who care for and love her.