"Dirty Blood" by Heather Hildenbrand.
This is the story of a girl, Tara, who kills a girl (a werewolf) one night and her life is never the same. People she thought she knew, she did not. She finds out she's a Hunter and that werewolves are real. There's a good bit of fighting, some training, and some average teenage antics. Of course there is a love interest, Wes, who is a great opposite to Tara. The characters are honest and true-to-life, except for the werewolf/hunter thing. It has a good plot and overall it's a good read. There are 4 more books to read (so far) in this series: "Cold Blood", "Blood Bond", "Blood Rule", and "Broken Blood".
You can find the author, Heather Hildenbrand, on-line in various spots. And she has 2 other series, Clone Chronicles and DreamKiller, the Specials.
Her blogspot blog
Facebook author page
Go check her out!