All's Fair in Love, War, and High School - Janette Rallison Darn, I did not know this was the 2nd book of a series.

Janette Rallison knows how to write YA books. And what it is the best of all is that her heroines are far from being a Mary Sue. Like in this book, Samantha is the typical blond, hot, popular cheerleader, and also shallow, and likes to insult people. But thanks to Logan, her ex-boyfriend, and her scores in SAT, she changes and becomes a better person.

As it happened in her other books, I liked the guy more than the girl -not that it means I did not like the girl, cuz I did!-. Logan is such a nice guy, and a bit of a tease too. Because he has a bet with Samantha (she could not insult people for 2 weeks straight) he gets closer to her and helps her improve.