granted it is a YA book
Do I have to defend YA even here??
Not to me -- I'm 33 and some of my favorite books would be classified as YA. I meant that, being 33, I may have seen certain phrases more often than a 13 year old would have: they may feel over-used to me but not to your intended audience. Plus there is a different psychology at work -- the idea of a "battle to control X" may resonate more deeply with a YA audience than it does with me. I don't think either of these statements requires YA to be defended (though feel free if you like, I always enjoy a good battle, er, discussion).
"As the Fey depart Corrine’s dreams, the battle for Hallowmere spills into day"
"The Fey depart Corrine’s dreams, but the battle for Hallowmere spills into day"
It's hard to do this without knowing the story -- each individual word becomes suspect. How/why do the Fey depart: do they flee; do they escape; do they attack/strike; etc.?
"The Fey escape Corrine’s dreams, and the battle for Hallowmere spills into day"
"Dreams of Fey [now] haunt Corrine [in|by] daylight, as a new battle for Hallowmere dawns"
MattD