The attack is the latest in a series by dangerous dogs across Liverpool, and sparked the ECHO's RSPCA-supported Biteback campaign for a change in the law.
Police and paramedics were called to Geraint Street just before 1.30pm on Friday after receiving 999 calls. The dog, believed to be a Staffordshire or pit bull terrier, had disappeared.
Police want witnesses to come forward as soon as possible. A spokesman said: "House-to-house inquiries have been carried out and police dog patrols have also provided a visible police presence to reassure the community".
An ambulance service spokesman said: "Paramedics provided as much medical support as they possibly could at the scene to stabilise her."
In May, eight-year-old Nikkita Douglas suffered terrible leg wounds when she was bitten by a pit bull. A month later, two bull mastiffs were shot by police after mauling a 42-year-old woman in Speke.
Last week, the ECHO reported on two further attacks, which saw Estelle Nolan, five, of Norris Green, and Owen Merrell, seven, of Runcorn, in hospital.
Our Biteback campaign, which calls for tough new laws and stricter punishments, was launched on the back of increasing concerns about thug owners using dogs to terrorise communities.