The fact that she feels the need to do this suggests that she probably does have some kind of mental health problem. I'm not excusing what she did, but no one seeks attention like this without some kind of underlying cause.
You need to look after yourself and do whats best for you. If you and your other friends that have noticed feel you can sit down and have a talk with her about it it would probably be good for her sake, but equally, it might be good for you to distance yourself from this friendship as,I can't imagine its particularly healthy for you.