In a very technical sense, she isn't. But her design pretty clearly takes from an Asian phenotype.Who says Sabine is Asian anyway?
But in the sense of Star Wars she's merely your average human, because when it comes down to it Humans are simply too far spread and have been for so long that determining such roots is... Kind of impossible.
So Sabine is technically just human, but has Asian traits to us.
How is she Asian if there is no (known) Asia in the Star Wars universe?