Face on a package of milk (book 1 from the Moloko series). Kuni Caroline B.

Jenny is the most ordinary teenage girl. She goes to school, chatting on the phone with her girlfriends, in love with a neighbor guy. She has an ideal house and loving parents. But once she sees the image of the missing girl on a box of milk and recognizes herself in her... Her whole life now seems to be a deception. She does not believe that her parents are able to kidnap the child. But why then they don’t show her birth certificate, there are no children's photographs in the house, and outwardly she does not look like mom and dad at all? She has to choose - pretend that nothing happened and forget about everything or solve this riddle and find out the whole truth about her past.