Strong second (?third) suggestion to read Rosalind Wiseman ("Queen Bees and Wannabees"). Her books, as well as "Odd Girl Out" by Rachel Simmons, are extremely helpful in opening one's eyes to the realities of "girlworld." Though these books do have chapters aimed at older girls and situations, there is a lot there that applies to all ages and they both have very useful practical suggestions and tips. They have been on my bedside table, literally, for years.