AHh she is in another relationship eh? That must suck...but you need to handle this maturely...sneak up behind him and stealh attack! J/k...either way tell her all of what you posted here...if she tells her BF just own him .
I suggest that you tell her, despite her having a boyfriend. Besides, the guy she's with is temporary, but you and her could be permanet. Don't procrastinate! Be hasteful! Tell her!
but be sure to do it at a time when you have her full attention. Don't just blurt it out at some random moment. Invite her over or ask her to join you in some sort of leisure outing then bring it up. Work your way up to it but make sure not to back down when the time comes. Tell yourself that you will not let the night end until you tell her what you want to say. Be confident. Girls love that.
Killing under the cloak of war is no different than murder