I would wear something like what you would wear on a first date to a casual restaurant. Maybe a polo, jean skirt, ballet flats, pearls...etc. Something where you're not going to feel out of place if you show up and everyone is wearing jeans and flipflops or skirts and heels.
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Facile remedium est ubertati; sterilia nullo labore vincuntur. I think pearls are lovely, especially when you need something to clutch. ~ AzTheta
The Real World Can't Hear You ~ GC Troll
Sororities want to recruit members who will not only be a good fit within the chapter, but also represent them well to the outside world. This includes a tidy appearance. Jeans and a cute top sound like they will work for an invitation to a casual event.
You're going on an interview by attending events at these sororities. So make a good first impression and look as nice as you can within the suggested dress code. Look your personal best. Good luck!!!
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hey! i would stick to an outfit that looks put together very nicely, express or guess have cute clothes as long as you choose conservatively. But have one item that really gives your outfit that wow factor. really cute shoes, a great necklace, or something so that you fit in with your outfit, but stand out with that one cute piece. good luck!