Habiba Mahmoud Mohamed, from the Manoufiya province, is believed to have contracted the potentially fatal virus after coming into contact with dead poultry. The girl started showing the first symptoms on Friday.
She is currently undergoing treatment at an Egyptian hospital.
Last week, a 2-year-old boy in Egypt's second-largest city of Alexandria was also diagnosed with bird flu.
Five cases of bird flu have been registered in Egypt this year, none of them were fatal. Egyptian officials have recorded 23 deaths from bird flu since 2006.
As of March 2, a total of 409 bird flu cases had been registered worldwide since the virus was first detected in 2003, resulting in 256 deaths, according to the WHO.
Although there have been no incidences of human-to-human infection, experts fear that the bird flu virus may mutate into a form that could be easily transmitted from person to person, causing a global pandemic.