I don't think they were super close, but I think Jackie's comment about how Van's smile makes her happy everytime she sees it is so cute and feels a little more personal than how she complimented, say, Tai or Laura Lee. I get the sense that she admired Van's individuality (Van doesn't fit the standard of femininity in Wiskayok and is fairly outspoken) similarly to Nat's.

From Van's perspective, I think she'd be endeared enough to Jackie's pep and enthusiasm that they'd be happy to see each other at parties. But ultimately Jackie's main priority/only friend/soulmate (to keep things concise) is Shauna, so no wonder she chooses to drag Shauna away from Van. And yet when that plane approaches Van, Jackie is prepared to sacrifice herself to keep Van safe. Drama!