Book 5, "Bad Hair Day", is one of my favourites in Sarah Mlynowski's Whatever After series!
Rapunzel is a sweet and shy girl who has a beautiful voice and loves her hair, but then Abby and Jonah travels through the magic mirror and accidentally ruin Rapunzel's hair trying to climb it. Now they're stuck in the tower with no way out.... They need to find a back door before Frau Gothel comes back with a ladder and shrink them to fingernail-size! Even if they manage to escape, how will Rapunzel find her happily ever after? <3