Alison Kennard, 42, of Norham Avenue, South Shields, must also pay the 14-year-old £500 compensation for failing to control the Staffordshire-type canine.
Magistrates heard the animal, named Tyson, ran from Kennard’s then home in Lincoln Road, Horsley Hill, South Shields, and attacked the youngster.
The girl has been left scarred after being bitten on the bottom, left thigh and ankle last New Year’s Eve.
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Kennard, also known as Bell, denied being responsible and had pleaded not guilty to being in charge of a dog dangerously out of control.
But she was found guilty after a trial last month and has now been told of the dog’s fate while being sentenced at South Tyneside Magistrates’ Court.
Magistrates rejected a plea by her solicitor Geoffrey Forrester for it to be spared on condition it is muzzled and kept on a lead when outside.
They said they were satisfied it remained a danger to the public - and ordered it be destroyed.
Prosecutor Ben Woodward said: “The injured party is a friend of the defendant’s daughter.
“They were in the friend’s garden. The victim describes Tyson running out of the front door and biting her.
“She stated that she did nothing to provoke the dog. To the defendant’s credit, she tried to remove Tyson. She also offered to go to the hospital with the girl.”
In a victim statement read to the court, the youngster said: “Since the incident, I’m now nervous at being around dogs.
“I’m also anxious that my scars and injuries heal properly. This could have been a tragedy.”
Mr Forrester said Kennard had suffered intruders at her home a few weeks before the attack.
He added: “The dog had reacted. In this case, there was noise at the front door and this has caused the dog to run out and bite. It’s not a reaction she could have foreseen.”
Mr Forrester said the girl had gone straight home and it was to Kennard’s credit she had followed and alerted her mother, who was unaware of the incident.
Magistrates also gave Kennard a six-month community order, with a requirement of 10 days of rehabilitation work with the Probation Service.