Normal Adolescent Behavior AKA Havoc 2 (2007)

Genres:Drama | Romance
Starring: Kelly Lynch, Amber Tamblyn, Daryl Sabara, and Kelli Garner

Plot:
Wendy and her friends avoid the heartless world of random hookups and friends-with-benefits by spending all their time together. When she meets Sean, Wendy is torn between her genuine affection and desire for him and her commitment to her friends, especially her best friend Billie: and Billie isn't interested in losing her friends.

http://www.imdb.com/title/tt0790721/
http://en.wikipedia.org/wiki/Normal_Adolescent_Behavior