I know someone with a big problem.?

There is a girl I know that I have known since she was in kindergarten. Were both adults now and she had a bad break down. She was crying and depressed and I had never seen her like this. She told me when she was 15 she had killed a bird, she had killed 4 birds in her life. She started killing cats she has killed three cats and she was upset and told me she had killed one last night. She asked me why God made her this way and I told her she needed to seek professional help. Now I know for a fact that she has never hurt a person, but now I'm terrified. I looked up her condition and found that she may have homicidal tendencies and I am not sure if I am in my right to say something to someone or what?? I don't know what do to help and I don't understand how a kind easy going person can do such a thing myself. I am overwhelmed and don't know what to do or who to talk to. Please, has anyone advice?