We're introduced to Maia, the biracial werewolf girl, in this book. She's had a rough life. Her brother Daniel abused her, and so did her first boyfriend, Jordan. Jordan is the one who turned into a werewolf. As a result, she "never trusted beautiful boys" (1.2.1).
This is pretty much just one more insult heaped upon Simon, whom she totally trusts. Sorry, Simon. You're not beautiful. She stops trusting Simon when he becomes a vampire, though, because werewolves and vampires just don't like each other. But eventually Maia realizes this is kind of bigoted, and we wouldn't be surprised if she and Simon hit it off in the next installment.