The saddest part about it is the scars it leaves...
Even when people get over it and stop doing it, they are constantly reminded of the time in their lives when things were bad. It's the same with suicide scars..the person is left with a line on their wrist as a reminder of something they would probably rather forget..
There's probably not a lot you can do about this girl corkie, if you aren't really close to her and don't really know her. Her friends might be able to get her the help she needs though.