In the Tinkerbell movies by Disney that give Tink her own story, she isn’t selfish exactly, more like headstrong, passionate and impulsive. She does not think things through.
The Disney site describes her as Sassy, feisty, fun loving. “Tink acts on her emotions and does not look before she leaps”.
OUAT might take her back to Barrie’s version, or the PP movie, but she does drink poison for peter in the play, so she is not selfish entirely. She just was jealous of Wendy.
“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass