Shay was just a tard future version of a hipster that wanted to go against the general standard.
She was probably just desperate, not David's fault some too cool for everything else girl fell in love with him

I'm sure she was blind to David not wanting her or whatever.
& Zane's brain was so fried after taking the cure that he probably couldn't even be mad at Tally for killing him.
So,

Anyways TOTALLY gonna re-read again.
I'll probably come back and have changed my mind ahaha.