The Sketchbook was trying to stop them from turning evil she even says herself now let's all agree to never be creative again, see that isn't what she wanted don't just assume she turned them bad. She even appears at the end of when the Fathers Day curse is lifted.
Red Guy sung the creative song in front of the crowd cause he likes the Sketchbook and thinks she's a good friend. She destroys the clown painting she thinks it'll turn to a killer clown. Shee says green is not a creative color, not saying she hates it if she does we don't know why.
When Red Guy summons all the teachers there's no Sketchbook cause Roy Dosent want her anymore cause she's a rebel against Roy, a friend and a misunderstood character.