Noel Sparks helped with the children's activities at Calvary Community Church in Westlake Village, her pastor said.
Rev Shawn Thornton said: "She loved kids. We had a lot of parents show up today to say, 'She made my child feel important and that they mattered.'"
The 21-year-old died when a former US Marine fired shots inside the Borderline Bar & Grill in the city of Thousand Oak - approximately 40 miles north west of Los Angeles.
Describing Noel as an "all-around good girl", her aunt Patricia Sparks of Morristown in Tennessee told The Associated Press: "We're in shock.
"She was the kind of girl that if you had friends, you'd want them to marry her."
Ms Sparks, who was also studying art at Moorpark College, often went to Borderline with friends and her mother.
A sheriff's sergeant who was the first police officer inside the bar during the attack was also among the victims.
Authorities believe the perpetrator, 28-year-old Ian David Long, killed himself.
Wednesday's incident - the worst mass shooting in the United States since 17 people died in a high school in Parkland, Florida nine months ago - comes less than a fortnight after a gunman killed eleven people at a synagogue in Pittsburgh.
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