Personally, I think all this talk of crime and punishment for the chapter is sort of silly. They took 3 extra girls during COB because their HQs told them to take to 150. It's 3 women!! It's not as if they had a huge keg party in their own house. Contact your local area advisor for collegiate panhellenics, which is available at
http://www.npcwomen.org/college/c_advisors.php, and tell them the situation. They can offer you suggestions and such, but a punishment view is just counter productive for a positive outcome. If you punish the sorority in question, they'll feel as if they've been punished for following an order of their HQs, if you punish the new women by not allowing them to initiate, etc., you hurt girls who want to be a part of your greek system. Talk to the greek advisor, and see what their view is. Talk about it at Panhellenic. I'm sure an amicable solution can be reached for all.