"Sitare Kadir Tema | 8. Bölüm Final Müziği" from O Kız is an instrumental piece by Cem Tuncer and Ercüment Orkut with no lyrics, but you can listen to it on YouTube . You can find the official soundtrack and videos at: YouTube (Sitare Kadir Tema) YouTube (Sitare)
For the theme song with lyrics by Yıldız Tilbe, you can visit: AZLyrics (O Kız) "Sitare Kadir Tema | 8