Charlotte Marsh-Jones, 21, of Frome Road, Trowbridge, was found guilty of grievous bodily harm following a trial at Swindon Crown Court.
The court heard that the incident happened on the evening of 29 November 2019 at The Sports Bar in Castle Street.
A customer went to use the female toilets but found that there were two people in the cubicle and complained to a member of the door staff.
The female member of staff found two women in the cubicle, and one of them was Marsh-Jones who appeared to be heavily intoxicated and had been sick.
After getting to her feet, she lunged towards the member of staff with a gin glass, causing a deep laceration to her victim’s face and neck, which was around 4 to 5 inches long from her cheek, through her ear and down her neck.
Marsh-Jones was restrained by door staff until the police arrived and she was subsequently arrested.
At the end of last month (30/07) she was sentenced to four years and three months in prison.
Detective Constable Simon Rogers, from Central CID, said: “This was an unprovoked attack on a member of door staff who received serious injuries.
“When asked to leave the premises, Marsh-Jones deliberately picked up a glass and struck it into the victim’s neck and face. The suspect continued to fight the victim who managed to detain her even after suffering the injury.
“This was a traumatic incident for all involved and I would like to thank the victim and witnesses for their evidence and support in this investigation.
“Her colleagues did a fantastic job of administering first aid and dealing with the aftermath before the police arrived.
“The victim was professionally carrying out her duties to keep the patrons of the premises safe. Violence such as this will not be tolerated and I welcome the sentence passed by the courts.”