Claus

Claus is a character exclusive to the 2003 anime, who lived in a village that the Elric brothers visited at the start of the anime during Edward's flashback. When they first met her, she was rude and acted like a tomboy who wished to avenge her sister's death who was killed by one of the Karin zombies. However, after being saved by the Elrics from Majhal's evil scheme who tried to use her as a sacrifice to bring back the real Karin (who unknown to Majhal was still alive), Claus warmed up to the Elric brothers and became more feminine. Something that shocked both Ed and Al as they originally thought she was a boy.