1. Expressing gratitude: Sincerely express gratitude to the girl, you can say "Thank you for the birthday cake, it's really surprising and happy
2. Share joy: Invite her to celebrate her birthday together, and if conditions permit, invite her to cut and eat cake together, sharing this sweetness and joy.
3. Giving back: Consider sending your own feelings or help at an appropriate time, such as her birthday, holiday, or when she needs help, to express your concern and gratitude for her.