Justin first comes into contact with Isabella when his friends from WizTech set him up on a blind date with her. At this point, he knows very little about her except what is on her WizFace (a wizard social network site) online profile.
Justin and Alex talk about how everyone lies on their profile, but when Isabella turns up at the apartment, she looks fairly normal. However, before long, she starts acting strange, such as growling and playing tug-of-war over Alex's sweater.
She kisses Justin and turns him into a werewolf. It can be concluded that she is a "mutt" werewolf. According to Mason, only mutts change humans into werewolves with a kiss.