DWAlphaGam -
I'm not sure how they got NPC to come. I think either the greek advisor requested it or NPC came on their own b/c they were noticing a few things about our recruitment: Large numbers of women were going through recruitment, but large numbers were also dropping out especially before and after pref parties. Only half the houses were taking quota, while smaller houses were taking only a few new members. Large houses were "padding their parties" and not making the cuts necessary to allow pnms the chance to look at other houses.
It's hard for me to remember all the details b/c it was so long ago. It did help that year. Unfortunately the following year we got a new panhellenic advisor and everything went back to the old way. Now my school seems to be losing a sorority every year.
I'd talk to an NPC representative or your panhellenic advisor if you feel that your recruitment could use some improvement. Hopefully they can help before the situation gets too bad.