"Hummingbird" by Natalie Lloyd

Natalie Lloyd's books continue to enchant and delight me.  And make me cry.  This one definitely made me cry multiple times toward the end -- but not over sad things!  Like with most books (and movies), what made me cry was some really, really good stuff happening against the odds that it wouldn't.
Like, not to spoil the ending or anything, but man, it is GOOD.  
Olive has "brittle bone disease," or osteogenesis imperfecta.  Because she's had so many broken bones all through her childhood, she's a...