Her Klan is "Dead in 30 Seconds" or DI30S.
She said her group would go to differing games to show their skills and the residents there would threaten them and some have even tracked people down to their houses and had to be removed by force. If you are the champ of Halo and some strangers show up to kick your butt, it seems to make them angry. There are films on Youtube showing this behavior. If I can find one I'll post it.
http://www.youtube.com/watch?v=95gCr6yAp3g&mode=related&search=
A klan of jihadi youth might think a tag like that was cool.