What do guys fight about? Girls. But Wei-Chen's girlfriend isn't your typical trophy piece, who Wei-Chen and Jin fight over. She's sensitive and smart and, like Jin, sick of being viewed like an outsider because of her race. Only she doesn't deal with her insecurity by wishing for whiteness—she deals with it by being real with her feelings.
You can't get any more honest than this: "'Today, when Timmy called me a… a chink, I realized… deep down inside… I kind of feel like that all the time'" (8.101). What she's saying is incredibly sad, but it's also authentic, deep, and revealing. Maybe that's why Jin kisses her—she says exactly what he feels, which can be a pretty powerful experience.
So Suzy's role may be small, but she also packs her own kind of punch. Literally too, like when she punches Jin in the face for kissing her (8.110). Don't turn to Suzy if you're looking for a repressed character—she's definitely into expressing her mind.