The unidentified 60-year-old woman was walking to her car in one of the parking lots when she was struck from behind and knocked to the ground. Culver City Police said the two girls stole the woman's purse and merchandise and fled on foot.
They were last seen running southbound on Sepulveda Boulevard.
Police said no weapon was used.
The woman was hospitalized with non-life-threatening injuries.
"The safety of our customers is paramount and always a priority for Westfield," said Westfield Los Angeles District General Manager Don Ziss in a statement on Tuesday. "As the matter to which you refer remains under active investigation, we must decline to comment. We are cooperating fully with the police department investigation."
City News Service contributed to this report.