Quistis Trepe is an eighteen-year-old instructor at Balamb Garden, where Squall, Zell, and Seifer are students. She uses a chain whip in battle, and her Limit Break, Blue Magic, a common ability found throughout the Final Fantasy games, allows her to imitate monsters' attacks. Early in the game, Quistis is discharged as an instructor because she "[lacks] leadership qualities". Afterwards, she maintains a more informal relationship with the other characters as a fellow member of SeeD.
Source: Wikipedia, "[en.wikipedia.org/wiki/Characters_of_Final_Fantasy_VIII%23Quistis_Trepe Characters of Final Fantasy VIII]", available under the CC-BY-SA License.