They were never really together. They kiss in the end of 2x08 and in 2x09 Jenny says Nate has been ignoring her since they kissed. They kinda get together during the episode, but split at the end of it. Then there's the letter Nate sends but Vanessa steals, so Jenny never gets to read it. And that's pretty much it, unfortanetely.
But there is more of them in season 3
3X09 Nate save Jenny from humilation
3x13 Jenny help Nate
3X16 Nate save Jenny from a bunch of guys in a bachelor party , Agnes did that to her
3x17 They hang out on his birthday , and J kinda kiss him
3x18 Serena and Carter are try to find s father, NS are Mad at each other, J is a shoulder for Nate to lean on
3x19 Chuck want his friend back, so he hook NJ together. But in the end of the episode, Nate ask Jenny to leave
