Not necessarily - a 14 year old wouldn't be showering with anyone else, and the rest of the time can wear long sleeves or a jacket. Not hard to hide if they don't want anyone to know, which is more of a concern IMO, and less likely to be an attention seeking thing.

I am quite 'highly strung' and I put a lot of pressure on myself to be what I consider to be perfect - when I was younger and I did something I felt was stupid or immature, I would cut myself as a punishment. The problem is, once the self harm starts, for whatever reason, generally the person is too numb to feel it properly, or get the personal reaction they're craving, so its not just one cut here or there, it progresses and gets worse.

IMO, if your DS has seen this girls scars/cuts, someone needs to know - parents, school counsellor, just someone close to her that can pull her back before its too late...