I'll share experience. I've got a female relative--let's say it's a niece; I've known her all my life as I am much older, and she showed signs of narcissism before the self-harm.
She has been given various diagnoses, starting with bipolar (inaccurate), then borderline (accurate but not much help) and finally Narcissistic Personality Disorder.
Her kind of "self-harm" is a bit different than someone cutting themselves, which to my knowledge she's never done. Rather, she eats to extreme, then starves herself and weight trains, back up with weight, back down... That, though, is more in the past.
Next, she would bait boyfriends, first choosing those likely to be easily pushed, and do things like break into one's apartment at 2:00 am and be waiting in the dark--almost got her shot as a burglar.
She would incite men to mistreat her, then play victim, i.e. go as an exclusive boyfriend's date to a party of his friends, all his friends, and then dance on all fours, on the floor, like a dog--dressed provocatively, then complain that he didn't return the money she had lent him.
There are so many stories like this. It's as though usually she cannot come right out and cut herself, though she did spend time in a crisis house for a suicide attempt she wasn't fully committed to, i.e. she needs attention badly--and if acting "bad" will get that, she'll take the beatings, literally or figuratively.
I know her history enough to say she was deprived of affection, slapped in the face for saying words she didn't understand like "sucker bite" and otherwise treated as just a pretty thing, i.e. nothing else to offer; not allowed or encouraged to be the best, more than a body and face.
Yes is the answer, yet underlying the question is something more profound, and to me, important:
How to help; who will see someone like this deep enough to find the little girl who needed to be respected, protected and loved... rather than treated as a thing to be valued for surface attractiveness.
She harbors, clearly, a lot of self-hatred, which she takes out on others at least as much as she takes out on herself.
I think of the Loving Friendliness Exercise: "May she be well, happy and peaceful. May no harm come to her. May she meet with spiritual success..."
That quote is from the book, Mindfulness in Plain English.
She has no true interest in therapy; in meditation; in any kind of help. Deep inside she doesn't feel worthy of it. I hope one day she can reach inside and come up with enough true self-love to begin untangling the twisted messages she received and internalized.