Tiese Shtolienen is Eugeo's former valet who learned swordsmanship under him. She is the eldest daughter of a 6th Class Noble family who entered the Sword Mastery Academy with an intent to rise her family status. She was a valet because she was one of the top 12 of her year, but she stated that it was not because she was a good swordswoman, but instead that it was because the entrance exam was on a Sacred Arts that she was good at.

Spoiler

After being saved from two nobles who were trying to rape her by Eugeo and Kirito, she falls in love with Eugeo.

(Source: Sword Art Online Wikia)