She was approached by a man in a park in Fauldhouse, West Lothian, before being forced into woods on Sunday, between 5pm and 8pm.
She returned home and police were contacted on Tuesday following the incident in the town's Eastfield Road area.
The suspect is described as white, 16 to 20 years-old, average height with a slim build. He was wearing a navy blue short-sleeved T-shirt, navy woolly hat and grey jogging bottoms
Detective Inspector Derek Long said: "Our enquiries into the full circumstances surrounding this incident are still at a very early stage."