Crazy girl says she'll kill herself?

Okay so this girl who was my "best friend" has been exposed. I have figured out she has lied about her age, identity, ethnicity, and basically everything to me and others. We figured out she is manipulative and goes around backstabbing us. Everything she says is a lie. She now makes claims she will kill herself, but it is not the first time. What should I do? and do you think she'll actually do it?