The Castle of Llyr (Pyrdain Chronicles)

Princess Eilonwy is growing up and must learn to act like a lady rather than a heroine among heroes. When Princess Eilonwy is sent to the Isle of Mona for training, she is bewitched by the evil enchantress Achren, so Taran and other friends must try to rescue her. Eilonwy of the red-gold hair, the Princess Eilonwy Daughter of Angharad Daughter of Regat of the Royal House of Llyr, was leaving Caer Dallben.