Leader of the Sylph race and an exceptional swordswoman. She was elected as the leader of the Sylph race by popular vote (80% voice of the vote). Her statistics are not very high due to her status as a Lord not allowing her to do much training. Despite her low stats, she is a formidable opponent in the Sylph dueling tournaments.

Spoiler

During a meeting with the Cait Sith, she is attacked by Salamanders led by General Eugene. At the same moment, Kirito flies in to challenge the intruder to a duel. After Kirito wins the battle, she attempts to seduce him along with Alicia Rue. Lyfa smothers their attempt, saying that he is accompanying her to the World Tree. At the end of the arc, Lady Sakuya leads a combined force of Cait Sith and Sylph against the World Tree in an attempt to aid Kirito along his journey.

(Source: SAO Wiki)