As long as you don't wear pink tights with sequins up the back, you'll be fine.
[Was that bad of me? Yes, very bad.]
Seriously, college is a time when a lot of twins start to come into their own and gain their own identity. It doesn't mean you love your sister any less. If you both follow your hearts, you'll be much happier and probably have better rush results than if you try and stick together. That may mean you both end up in the same sorority, or maybe different sororities, or maybe one or both of you find out it's not for you. It can't hurt to try, though.