It wasn't the storyline. I think Dessen did a great job of showing Colie's transformation from beaten down to confident. It was the supporting characters that spoiled the overall effect. So please forgive the following rant.
Secondly, Norman. I get that he was "disowned" by his dad because he wants to be an artist. I get that he lives in Mira's basement because of that. But how old is he? I'm figuring he's in college and is twenty at least, which would put him out of the way as a love interest for Colie. Nope, not the case. Let's just drop in, two-thirds of the way through the book, that he is only 17 and therefore "perfect" for Colie. You can't throw that in there after I think I already have this character figured out. Tell me earlier, so it's not out of the blue that he has a crush on her!
I also loved how Dessen describes how it feels to be bullied. I've been there. I can relate, and I'd guess a lot of her high school readers could as well. And I loved the message of the book - you don't have to take it. You are a valuable person, and you can be confident in who you are.