A 29-year-old man who was in the apartment has been arrested on suspicion of attempted rape.
Police were called to the scene just after 11pm on Friday. By the time they arrived along with other emergency services, the woman had already managed to get some way away from the apartment by herself.
She was still conscious and was taken to hospital. On Saturday morning she was being treated in intensive care.
According to what the 18-year-old told police, she was visiting another apartment in the building on Friday evening. When she went outside for a cigarette a man started talking to her before forcing her up to his apartment.
The woman said she felt threatened and had no other choice but to try to escape out of the window.