Authorities said the incident happened around 6 p.m. on Dec. 5 at a Bank of America in the 2300 block of Borchard Road.
The suspect entered the bank, approached a teller and passed a note demanding money. The teller walked away and informed other employees who activated the bank's alarm system, authorities said.
Authorities said the suspect left the bank and believe she fled in a dark-colored vehicle. She is described as standing 5 feet 7 inches tall, with a thin build and brown eyes, between the age of 20 and 30 years old.
Ventura County Crime Stoppers is offering up to a $1,000 reward for information that can lead to the arrest and conviction against the suspect.
Anyone with more information was urged to call Detective James Sullivan at (805) 947-8109. Those wishing to remain anonymous may call Crime Stoppers at (800) 222-8477.