Which of the pop girls had the best era-ending single from their most-recently-completed eras?
Some choices (but you aren't limited to these):
Britney Spears - Criminal
Demi Lovato - Give Your Heart A Break
Katy Perry - Wide Awake
Ke$ha f/ will.i.am - Crazy Kids
Lady Gaga - Marry The Night
P!nk f/ Lily Allen - True Love
Rihanna - What Now