Does my teenaged cousin have a mental disorder?

My cousin Lia is 14 years old and I catch her doing weird stuff all the time. Sometimes she would be in her room listening to her ipod and spinning around in circles on her computer chair in the dark. Sometimes I catch her talking to herself and saying stuff that characters say on tv. And sometimes she runs around in circles in her room while listening to her ipod. I asked her about all this stuff and she told me that she pretends or imagines that she's someone else. She said she imagines being a diffrent person with a diffrent life and she showed me notebooks where she has written down details and stories about this person that she imagines being. She said that when she's running around or talking to herself she's being someone else and that for years she's been spending all her time imagining herself as a diffrent person.she calls her 'alter ego' ashley and she said that she doesn't kno how to be herself, that she wants to be ashley and that she's not herselt. Evrything she does or says is what ashley would do or say. This is all soo weird to me I feel crazy jus trying to explain it. Lia also has been really depressed Lia's tried to kill herself and she says she hates who she is. She has bad hygiene she's antisocial and all she likes to do is listen to music and get on the computer.. Do you think something is wrong with her mentally? What should I do?