From what I've read, her defense (should her case remain in adult court), will attempt an insanity plea. A witness who talked to her the night of the murder said she was having suicidal and homicidal thoughts at the time. She made no attempt to cover up the crime; in fact she called police and confessed and then apparently acted oddly when they arrived. All these speak to a potential mental illness at the time of the murder. But insanity is much harder (and has much stricter criteria) to prove than a mental illness.