The girl, identified as Iovuta, was last seen on Saturday, March 14th, Vaud cantonal police said in a statement released on Thursday.
Her parents have not heard from her since that date.
Police describe the girl, a resident of Romania, as 160 centimetres tall, of slight build, with long dark hair.
On Saturday, she was wearing blue jeans and a pullover.
Police said she may also have been wearing a white neckpiece.
Anyone with possible information about her whereabouts is asked to contact Vaud cantonal police on 021 644 44 44 or via the nearest police station.