I absolutely second both. (With the caveat that 'The Egypt Game' scared the hell out of me, although I also loved it.)

Most of my recs for that age are for classic British children's literature, which it sounds like this girl might not be in the mood for (just going on the fact that she's reading twilight and not harry potter--I have reams of stuff to give people who are into harry potter). Snyder and Konigsberg are now historical (eep!) with stuff set in the 70s and maybe early 80s, but they are American and I think would still feel pretty contemporary.