My friend self harms after me?

i started self harming because my dad killed himself in the army. my friend saw my cuts and scars, she came round my house one night and asked me how it do it. so i said i used a pair of scisors. she grabed hold of them and writen her name on her arm with the scisors. she is showing it of to the whole school. she has started self harming plainly for attention. how do i stop her from doing this.