Create a cozy and private environment for her to share. Maybe have a quiet dinner at home with soft music in the background. Let her know that whatever she shares stays between you two. If she starts to share a story about her first heartbreak, don't rush to give advice right away. Just be there for her, hold her hand, and let her pour out her feelings. This will make her feel safe and more likely to share more stories in the future.
Be open and share your own first - time stories too. It creates a sense of equality. If you share your first time trying a new sport and how clumsy you were, she might feel more at ease to share her own experiences. Also, don't judge. If her story is about something that didn't go so well, like her first job interview that was a disaster, don't criticize but instead offer support and say something like 'It's okay, everyone has those moments.'