Joy Zhang, 21, was at the lake with a Douglas College program for students with development disabilities, when she and another student told staff they were going for a walk around the lake.
The second woman was found by searchers late Thursday night, but so far Zhang had not been found.
Searchers were hoping she spent the night sleeping and they will be able to find her in the daylight.
But by noon Friday, there was still no sign of Zhang, despite a massive search involving more than a dozen people on the ground and by helicopter, according to Coquitlam Search and Rescue coordinator Dwight Yochim.
Officials from the college say Zhang has the mental capacity of a 10-year-old, but it was not unusual for the students in the job placement program to go off on their own unsupervised.
Zhang did have her own cellphone but left it in a backpack on the beach. She is described as Asian, five-foot seven-inches tall, 100 pounds, wearing Capri style pants and a pink jacket.
Her distraught parents have been at the search site hoping for the safe return of their daughter.