Songs for a 12 year old to have on her iPod?

The girl that I babysit for isn't a baby, believe me. She is very mature for her age and listens to artists like Katy Perry, some Kesha, and the Glee cast (she also watches Glee.) She recently got 3 Glee CDs and $30 in iTunes gift cards, which she decided to use to completely revamp her iPod. She says it had artists like Miley Cyrus, Selena Gomez, and other 'Disney' artists on it that she thought were babyish, She asked me if I had any ideas for her. Please don't suggest any of the Disney stars or Justin Bieber (she hates them. xD) She listened to one of her friend's iPods and liked some of the songs they had on it- any suggestions? Even if it's just one suggestion, that would be great. Thanks so much! :)