Bloodline by Richelle Mead
You meet Sydney Sage, who apparently played a minor role in the Vampire Academy series, who is sent on a mission to redeem herself after assisting vampires despite the fact that she is an Alchemist. Needless to say, they are supposed to hate vampires.
There she meets Jill, Lissa's sister from the original book series. She has gone into hiding after an attempt at her life at a council meeting.
Her job is to make sure that Jill isn't discovered as a vampire. She runs into some trouble though with Adrian, another character from the original series, someone who she instantly does not get along with.
The story follows her journey along with Jill and Adrian.
Now, in my opinion, I think there is an undeniable attraction between Adrian and Sydney, though it isn't really all that apparent until the end. But the development of the characters, and the characters themselves are loveable.
I certainly mean to continue on with this series, the next book being Golden Lily. I hope there are some more Adrian and Sydney moments in the next book :)
P.S: I have been having trouble finding good books to read lately, so if you have any good Teen Fantasy type books like the ones I've already read I would love to hear from you :)