Does she have to play an instrument too as she only has started keyboard /guitar lessons.
As for composition, they get given a type of music that they have to compose. My daughter did a minimalism composition and an African drumming composition. The teachers will give you tips and feedback, so you can perfect your composition before it is sent off for marking. I think they also got sent off in y 11 so plenty of time.
I can recommend the cgp music revision guide.