While the story itself is tragic I can see why it's a good tale to pass on:
1. Highlights the need to not be quick to judgement
2. While the girl knew she was receiving unjust treatment, she bravely endured even to death to save people's lives. While you can just slap a martyr label on her, I think you could also interpret her as a symbol of love, compassion and courage. She had to really love others at heart to be willing to go that far for them. If the people had imitated her qualities, she wouldn't have met such a sad end.
3. The flowers blooming on her grave could symbolize something beautiful being able to come from hardship/tragedy. Maybe bringing to mind the idea of hope and resiliency.