What I Saw and How I Lied is told entirely from the perspective of our sweet young protagonist, Evie Spooner. The first person perspective allows us to see all aspects of the story from Evie's perspective, which means that we only see what Evie sees.
So when Evie sees that Peter Coleridge is a handsome young man who is flirting with her—and might even be interested in a relationship with her—we take this at face value. Even though we're along for the ride when Evie and her mom go for long car rides with Peter Coleridge, we fail to notice the sparks between Peter and Bev because Evie doesn't recognize them either.
Because the story comes from Evie's perspective, we also get to see how her point of view matures over time. At the beginning, she is pretty much a naïve little girl, but by the end she's experienced some tough stuff that makes her reevaluate her family, the injustices in the world, and even how she sees herself. And as her eyes open, ours do right along with her.