This is Macy's story through and through. And we're not complaining—after all, we kind of like the girl.
Seeing the story through her eyes allows us to connect with our leading lady in a way we couldn't if we were looking at things from the outside. Let's take a quick look at a quote to show you what we mean:
It took a lot of work to be perfect. (1.8)
If that came from a third-person narrator, we'd probably just think "yep, that's true," and move on. But since it comes from our protagonist, we just want to reach out and give her a hug right from the start. We want to tell her, "it's okay to mess up." Because, by the way, it totally is.
But a first-person narrator isn't all roses. After all, Macy is also a little emotionally drained at the moment. Add that to the fact that she's telling a story about her own stinkin' life, and you get a narrator who doesn't quite see things objectively all the time. Like, come on, we all knew Jason was a jerk long before she did, and we just have to wait for her to come around and join the masses.