Disclaimer: I don't own Once or any of its characters, nor do I own Peter Pan or any of its characters.
I wrote this as a one shot for Peter Pan and Tinkerbell, because we are never told exactly what goes on between them.
She still is crying after what Blue told her. She is angry with blue, with Regina, but mostly with herself. She never should have disobeyed Blue and tried to help the evil queen. She knows that running away was the right decision; she can't bear the sadness and the grief though.
He hears something; no one is able to get on or off the island without him knowing. It sounds like someone crying. He takes a step closer to it, only to hear it stop and the muttering of words to replace her soft sobs. He rounds the corner, coming to a stop as he sees a blond beauty.
She turns as she hears a twig snap behind her. A boy, no older than 16, comes into view. And she realizes how his hair blows softly in the picking up wind and how his face looked kind, but somehow rough. She sees through his eyes and into his soul, for she has always had that gift, and she knows he is troubled and has hardship in his past. She can see his mistakes and his evil, but she can see the slow change he has made. She is able to read his thoughts, and his thoughts make her blush such a deep red that one would think her color is scarlet instead of green.
He, on the other hand, can't see what her problem is. He asks her "Why are you here?" (Of course he is no longer thinking the scarlet inducing thoughts but rather how a simple girl could get into Neverland without him knowing.)
She answers "I ran away, I didn't know where to go so I came here." She decided not to tell him that she probably would be banished anyway.
He laughs and says "Well then you have come to the right place, but I must warn you that you can't come into camp because we are a boy's only group."
"Is that so, well then I suppose I can just stay out here; out of sight out of mind."
But he knew she wouldn't be able to escape his mind. And it was only a matter of time before they would be kissing in the moonlight.
And so it was, they fell in love slowly and then all at once; but he knew he would have to let her go. An argument is what separated them, they were arguing about whether or not revenge was really worth it. That's why Tinkerbell couldn't bring herself to crush Regina's heart, because revenge was and is never worth it. Others' need for revenge had hurt her twice, she didn't want to hurt someone else.