It could be about a girl who is on the verge of some major life change or crisis. Maybe she's on the edge of making a difficult decision like leaving home, choosing a career path, or dealing with a personal trauma. Since it's based on a true story, it might draw from real - life experiences of a girl who faced such challenges.
Well, often when a story is titled 'Girl on the Edge' based on a true story, it can involve a young woman who is in a precarious situation. It could be related to her mental health, for example, she might be on the edge of a breakdown due to various stressors in her life such as family problems, school bullying, or social isolation. The fact that it's based on a true story makes it all the more poignant as it reflects real - life struggles that many girls might face.