Meghan Darcy Melnyk, 28, pleaded guilty to robbing a Servus Credit Union in February.
She also pleaded guilty to fraud and breach of probation charges.
She is free on bail until her sentencing hearing.
Outside court, Melnyk said she's ashamed and feels horrible for what her family and her former university have been through.
She said she's at a loss to explain why she robbed a bank with a disguise and a weapon.
"It felt like it was a different person. I mean, I know it's me but it didn't feel like me," said Melnyk, who admitted she has a gambling problem.
During the robbery, Melnyk approached a teller at a Servus Credit Union in the southeast end of the city, indicated she had a weapon and left with an undisclosed amount of cash.
A police helicopter later helped locate her vehicle and tactical officers took her into custody.
The fraud charge had to do with stolen cheques in 2010.
Melnyk resigned as student president at the end of January.