The angry bees attacked both drivers as they got out to exchange information in the 2000 block of Los Amigos Street in La Canada Flintridge, sheriff's Sgt. Jose Larios said.
The older woman, fearing for her life, ran into the rear of a residence and jumped into a swimming pool to escape the swarming hordes. Firefighters rescued her.
The teen, meanwhile, fell to the street.
Los Angeles County Sheriff's Deputy Chad Pluimer used a fire extinguisher to get the swarm off the girl.
"She was just covered in bees," Pluimer said, "so I retrieved the fire extinguisher from my trunk. I told her, 'Close your eyes and hold your breath,' and I sprayed her with it just to try to get the bees off of her."
He helped the girl upand they both ran to safety. Pluimer then used the hose from a nearby home to remove the rest of the bees from the teen.
She was stung about 50 times.
Both were taken to a hospital for treatment. The deputy was also stung, but not taken to a hospital.
The hive was removed by a local pest control company.
Firefighters sprayed foam to keep the bees at bay prior to the pest control company's arrival.
Doctor Armand Dorian, who works at the hospital where the woman is recovering, said 1,000 bee stings could kill a person. But these kinds of attacks are rare.
When they happen, experts say, it's best to close your eyes and cover your mouth and ears and run.
So far experts have not determined if the bees were aggressive Africanized bees, also called "killer bees."