how can a local become national?

[Greekgal7]

ok.. my sorority had been around since 1984 at my college and was asked to do either of the following: become a national (keep our sorority letters, and become a national without combining with other sorority); or combine with another national sorority which is the Sigma Sigma Sigma and become part of that sorority; or shut down the chapter entirely.

We, as the first option, want to become national without combining with another national sorority and have the NPC to add us (our sorirty letters) to their other fellow chapters.

any ideas how this works