I personally really love Nick/Sally, but I can see where the Nays and Heys are coming from.
The appeal for me is mostly that I adore them both and want them to be happy. I feel like their personalities mesh really well? They’re both fun, positive people with ~hidden burdens~, and I enjoy how those shared aspects of their characters reflect each other - that Sally’s optimism is learned and deliberate, for example while Nick more or less comes by it naturally. The anecdote about Nick teasing Sally with yawns is the cutest thing in the world.
But yeah, they don’t really interact “live in front of us”, so to speak; what we know about their relationship feels really ambiguous and can be read multiple ways.
For example, when Sally confesses to Nick in the hospital, she talks about how frustrated she is that her crush makes her act like a different person around him. I find this HIGHLY relatable. That they can only communicate through stilted, formalised sarcasm while harbouring intense romantic feelings is frankly completely delicious and hilarious. The tension! The banter! The pining! It’s another big part of why I love them together.
But in the absence actually seeing that dynamic play out, it’s easy to take this as an indication that they’re simply not close - and therefore it’s weird that she’s visiting him in the hospital while he’s unconscious, possibly at the expense of his actual sibling, etc. On the other hand, I personally read it as “Sally is a close long-term family friend and should be able to visit Nick regardless of romantic attachment because they’re significant presences in each other’s lives”
I don’t see Sally as childish at all, but I think maybe part of that perception is that a lot of her introduction is in Button’s childhood flashbacks. So maybe if her establishing flashbacks were set between high school and Aeon, they might shed more light on who she is now as an adult + set up her current relationships to Button and Nick?
That seems like. Kind of a horrifying massive undertaking though.
Whoof, I hope literally any of that made sense.
Ps: YAY thank you for letting me not eavesdrop! I always feel so bad and guilty lol.
Edit: eek spoilers