Charlotte Goode was drunk when she clashed with Paige Sartin at the Makoto Bar in Bridge Street, Walsall, during the early hours of January 6.
They did not know each other but appeared to have a short conversation before violence flared, Wolverhampton Crown Court heard.
The defendant reached out to a nearby ledge, picked up a glass and smashed it into the face of the other woman, revealed Mr Tariq Shakoor, prosecuting.
Goode then tried to hit Ms Sartin again but was prevented from doing so by other customers, it was said.
The injured party was cut above the right eye, near her lip and on both the nose and the right side of the face, the court was told. Police were called and Goode was arrested at the scene.
Ms Rebecca Wade, defending, said: "She accepts that what she did was deeply unpleasant and has caused the injured party pain, trauma and scarring.
"She has not tried to minimise her role in leaving a woman with permanent facial scarring.
"This case was a real wake up call sending her to seek medical assistance and dramatically reduce her alcohol intake.
"She has shown considerable remorse and is living with her parents who support her but do not condone her behaviour."
Goode, from Coronation Road, Shelfield, pleaded guilty to wounding and was jailed by Judge Simon Ward who told her: "Maybe Miss Sartin said something but, as you accept, that certainly would not excuse you putting a glass in her face, causing the young woman permanent disfigurement."