Eirika (Erika in the Italian version) is a playable character and a protagonist in Fire Emblem: The Sacred Stones. She is the only daughter of King Fado of Renais, and the younger twin sister of Prince Ephraim. She is the princess of Renais (or if she has an A level support with Innes, the queen consort of Frelia).
Eirika appears as a Sticker in Super Smash Bros. Brawl, and also appears as a DLC character in Fire Emblem Awakening.
(Source: Fire Emblem Wikia)