Mac

Mac was raised in a small town and was a fairly average, quiet, well behaved girl most of her life. She was bullied for some of her oddities, with a mutual friend of hers taking particular joy in tormenting her. A boy a year above her offered her a way to get back at her tormenter, pricking his finger and telling her to prick hers and touch them together to let the blood mix. She didn't think much of it until she was walking home and found herself on her bully's path. The next thing she could remember was waking up coated in the bully's blood. The boy who had given her lycanthropy offered her protection if she joined his pack and she found herself hanging out with her high school's outcasts. 

She became close friends with another girl in her grade and developed a bit of a crush on her, which she was stifled from exploring by the boy who had invited her to the pack. He staged a coup against the pack's leader and took over, then used his position to pressure her into a relationship. One day while hanging out with the girl she had befriended they ended up kissing, and when the pack leader got wind of it he ended up killing her to get back at Mac. Made stupid by rage and unwillingly to involve the authorities, she shoplifted a silver knife and stabbed him in his sleep, then chopped off all her hair and ran away from home.

One day, while feeding off a deer carcass, in the woods, she met an older werewolf who offered to give her a job and a place to stay. She was referred to the Wolfsbane Institute and hired under an "off the books" contract used for unregistered werewolves. Since then she's worked as a security guard, protecting the very people working to eradicate her kind.