this might sound kind of dorky, i dont know what the PNMs are like at your school, but maybe one approach would be to pump the benefits of all the alumnae? a lot of girls from my chapter have gotten help and recommendations from fellow phi sigs during their job searches. i know i plan on breaking out the alumnae directory when i start looking next year!
another thing might be to talk about sending girls to convention every summer, and getting to play with other phi sigs from different chapters. plus you could talk about how nationals is always there to provide support in case something goes wrong, whereas locals get kind of screwed if they get in trouble.
we dont really have any locals at my school, so i dont know what it's like to have to actively compete against them, but hopefully this helps?