The nurse has been released from hospital and is recovering at home.
The union calls it a serious attack on the female nurse, adding that it's the second incident at the facility in four months.
"The fact that another nurse has been hurt while trying to provide safe patient care underscores the urgent need to make work sites safer," said B.C. Nurses' Union President Gayle Duteil.
B.C. Health Minister Terry Lake says he has spoken with the union and plans to meet with them and hospital staff on Friday morning.
"No one should go to work and expect that they will suffer violence in the workplace," said Lake. "We are determined to reduce this type of incident."
Lake said that the Hillside Centre was identified as a high-risk facility at a summit that took place in Vancouver last week on violence prevention.
Other high-risk facilities identified were the Forensic Psychiatric Unit in Port Coquitlam, the Seven Oaks Tertiary Mental Health in Victoria and the Abbotsford Regional Hospital.
"Certain facilities, such as psychiatric facilities, experience greater challenges when it comes to workplace violence," said Lake in a written statement.
"They care for some of the most complex, and sometimes unpredictable, patients, and we need to take a close look at these facilities."
The Hillside Psychiatric Centre is a 44-bed facility at the Royal Inlands Hospital that serves adults and elderly individuals with acute illness and/or severely dysfunctional behaviours.