Omg what is this I totally ship Abby/Leah. I want this to be canon. And as for Nick/Nora, I can't believe you wrote a straight ship! :P They are cute though, especially as they seem to have a lot more in common than Nick and Abby did. I like that they bond over music, and Nick’s description of how his view of Nora went from Simon’s younger sister to being interesting on her own.
But I did really sympathize with Nick in the beginning when he was the only single person there and while he's happy for his friends, the fact that they're all coupled off makes him feel really lonely. Especially for New Years. And his thoughts about how the dynamics of his friend group has changed were kinda sad, but also very high-school – it felt really true. So it was sweet that he ended up finding Nora and she's by herself singing a song which is kind of about loneliness, and that they can share that. It was a really cute scene.
Last but not least, Drunk Simon (from one beer) is hilarious. Great story!