Hey sis!
Since I'm not in an NPC sorority I am of limited help. But from reading threads on here, I *believe* that a few things must happen. First, all the houses at your college must be at quota (am I right, or somewhat right?)...there must be a need for a new NPC. In addition, AEPhi, SDT or any other Jewish sorority also must be interested in chartering there.
I would talk to your Greek Affairs office as others have suggested. They could offer you the most help. Then I would try contacting SDT/AEPhi.
Either way, I'm pretty sure that to get a chapter of an NPC, you usually form a local first with an intent to affiliate. Why not working on plans for a local Jewish sorority then?
If worse comes to worse and you don't end up affiliating with a Jewish NPC, you would still have the Jewish sisterhood you feel the need for.
Hope this helps, hon. Let us know if there's any updates!
Love & roses!