Double Dare You (Ella Diaries #1) by Meredith Costain

WARNING:
You are about to read my UTTERLY BIGGEST SECRETS.
Can I trust you? OK then. I'm Ella, and this is my diary.

It's a new school year, and it's perfect. Until class starts that is, and EVERYTHING goes wrong. Ella can't believe that her absolutely WORST ENEMY EVER, Peach, is sitting next to her! No matter how far Ella moves her new pencil case across the desk, Peach is IN HER SPACE. Where's her BFF Zoe?
How can this year get ANY WORSE?