My Emily is 4 1/2. When she was about 2 1/2 or almost 3, she had picked a dandelion to give me. When she noticed that I had taken it out of it's glass on the counter and thrown it away, I explained that it had died. She immediately asked if it had CF and was that why it died.
That broke my heart.
She asks questions about CF as they come up. Mostly the "Why" questions. Why do enzymes work? Why doesn't pulmozyme smell like albuterol? Why does it matter if my poop sinks or floats?
We give her truthful answers as best we can, in words she understands. We try not to dumb it down.
When we talk to other people about anything CF related, she tends to plug her ears and do the "nah nah, I'm not listening" thing, but by now we all laugh when she does it, and it's become her little joke.
My goal is to be open and honest about it, and to let her know that it's fine to ask questions, to have fears, to be angry, to talk to other people about it.
My guess is it won't be long before your little one has questions or comments. You're already teaching her that it's a part of her life...just go with that.
Good luck!