RCMP say the staffer suffered minor injuries when the attack allegedly occurred Saturday evening at a facility in Didsbury.
They say the trio confined the worker and took a van belonging to the home.
One of the suspects later turned herself in to Calgary police.
Mounties are looking for two girls, age 15 and 16, who they say should not be approached if anyone in the public spots them.
The van is a silver 2007 Toyota Sienna with Alberta licence number 89H783.Suggest a correction