D.,
My best advice to you at this point is to slow down. May is a little word with a whole lot of meaning. She MAY be a genius, and she MAY grow up to become president. Then again, she MAY not. There is also a world of difference between HAVING cystic fibrosis, and CARRYING the gene for it. That second one isn't an issue for her at all until it's time to decide if she wants to have kids of her own.
It sounds like you need to have further testing done. Talk to the pediatrician, or the specialist who gave you this information. Ask for a complete walk-through of all the upcoming steps to determine a diagnosis. Make them go slow, and explain each part until you are completely confident you understand. The Doctors work for you. They are paid service providers, no different than a plumber or hairstylist. They provide a service, and you give them money. That's it. If you don't like the service they are providing, or their attitude while they do it, fire them and hire someone else. DO NOT let them intimidate you, or rush you. You are in the driver's seat here.
Once you find out where your daughter stands, then it is time to get educated. If she has CF, there are great resources on the Net that will explain her condition, the prognosis, and all of the issues with her care. You can also turn to the web for help finding other Moms who have dealt with this same thing, and can help you out. Even a special needs parents' suport group will be a great resource, because those people know the feelings of fear and helplessness that comes with dealing with this kind of challenge.
Hold on D.. I can't imagine a fear in the world more potent than a sick child. My heart goes out to you, and I hope for the very best results from the upcoming tests.