Your friend is having a problem with rejection. She needs to work with a therapist to find out where this comes from in her. Her choosing to lash out at these other individuals will never fix or heal what is in her that brings these resentments on. Her choosing to try and ruin or cause pain etc will just end up causing her to be rejected even more. Unfortunately, if she is a narcissist, she probably won't be receptive to actually healing instead of engaging in lashing out.