Why not ask your Diamond Sister to set you up with a friend of hers? I'm sure she knows a guy who'd love to go with you. Plus, if her date and yours are brothers or even just friends, then there is a way to hang out with your Diamond for the night (without is being just one-on-one). OR, ask your President, NMC, or other older sister. I'm sure any sister would be thrilled to set you up!!
At my chapter, sisters would ask if anyone was in need of a date and then introduce them to a guy-friend that wanted to go to our formal. (ALL the guys wanted to go to the ADPi events!

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