If a person does this and requires attention, then suddenly, he needs this attention.
Cutting veins has an addiction mechanism, when cuts are released hormones and a person becomes better. This behavior is a sign of depression. Try to talk to your friend about her problems and difficulties. Convince her that there is no need for this.
If you do not feel confident in yourself - refer to an unobtrusive psychotherapist. Explain to her that you are worried and that it will make her feel better and calmer. Go with her. Develop her fears of going to specialists.
And about ignoring such people, I have a story.
My classmate's father showed similar inclinations. Including made feigned suicide attempts, allowing himself to be saved. The family did not accept him, they said that he just wanted attention and was fooling everyone. I would like to commit suicide - I would have done it long ago (a typical opinion for the CIS).
Recently I saw my classmate. His father hanged himself on the cabinet handle (it is very difficult) right in the apartment, literally strangling himself with a rope. The family considers themselves to be responsible for his death. And not only them.
I hope your friend is not so bad, but still pay attention to the problem.
Many people think in such cases that the "rezun" has some kind of mystical "reservoir" of attention and something there, it needs to be "filled" periodically and the problem will disappear.
Logic is this curve ; it’s just an unhealthy habit, and she has only one solution: leave your friend alone and do not react in any way except distance. There is no need to reinforce useless behavior - if, as a result of such actions, she still receives attention (and most often it does, especially with loved ones), then she will not have any motive to stop and learn methods of attraction later.
Want to help? If you are not a psychiatrist or a psychologist, I do not advise, it is better to refer to specialists. All that you can do on the part of a friend is to pose the question only with such a "edge": either this matter ends, or we do not communicate until it stops. Naturally, if your friend doesn't really need you, then it won't give any effect, but still.
No need to react. They do this to attract attention to themselves. You react. She is pleased. And do not listen to the previous responder, the child is talking nonsense.