My cm was going to get chickens and I was worried too. I think I'd have to think hard about it personally, particulary as I can remember my Dad catching psitticosis from the birds he kept (parrots and chickens) he nearly died, so I guess I am slightly paranoid when it comes to any sort of bird - with or without bird flu thrown in the mix.
She'll be fine, we were brought up on a farm, my grandparents had chickens, as do some of my friends, the same rules apply; wash hands after touching them and as the other poster said, she'll love looking for eggs and it's a wonderful experience for her.
Parrots are a worry for psitticosis, but I don't think chickens are, don't quote me tho'.
Chickens really aren't that much fun to play with. You can feed them, collect eggs, chase them, get them to follow you, but you'd hardly play with them in the same close way as you would a dog or rabbit.