Carol Berner had asked a three-judge panel of the B.C. Court of Appeal to overturn the two-and-a-half year sentence imposed in the death of Alexa Middelaer, who was feeding a horse by the side of the road when she was struck in 2008.
The judges conferred briefly before returning to say the appeal was dismissed and they would deliver their reasons at a later date.
Berner could still file another appeal with the Supreme Court of Canada, but she must start serving her sentence immediately.
Alexa's father, Michael, says he expects Berner to continue her appeals, which he says have now dragged on longer than his daughter was alive.
On Wednesday, Canada's highest court refused to hear a separate appeal from Berner aimed at overturning her conviction. (CKNW,News1130)