Hey Asia,
That's great to hear! Congrats!
As far as what to do when the sorority's Prez comes to visit you, I think Equeen made some good suggestions. Just be yourselves and everything will be just fine.
I would also find out whether or not it's going to be purely social or if it's going to be a mix of sisterhood/business. I would say that if it's going to be a mix, you can surely utilize this time to ask questions about the organization and the process itself.
Other ideas....I think it would be a good idea to take her around campus and give her a brief history of your school (ie traditions, student life, etc). Then maybe you all can treat her dinner if that's in the budget. Another idea would be to find a cute way to tell her about yourselves and what you've been doing thus far to become a part of the sorority...maybe in the form of a skit or something like that. I don't know, just something creative and fun to do.
Well I hope you have fun! And try not to worry (yeah right!) it's all going to work out just fine.