The victim of the attack suffered a broken nose, ripped ear and a flap of skin was torn from the left side of her nose. One of the dog's teeth had also pierced through the girl's cheek.

Kristy Pearce, of Queanbeyan, advertised her pet dog named "Storm" on the classified website Gumtree in January.

This was despite receiving a letter from Queanbeyan City Council advising her that they intended to declare Storm as a dangerous dog following an alleged attack.

In the ad Storm was described as "a big lovable bear although might not be good around small children due to his size".

Pearce, 27, had inherited the dog from her sister who adopted the animal from a pound in the ACT. However, her sister found the dog to be too boisterous and loud around her children.

A man agreed to take the dog on February 2. Just 10 days later the dog attacked his teenage daughter.

Pearce pleaded guilty to advertising the sale of a proposed dangerous dog at Queanbeyan Local Court on Monday, December 9.

She also pleaded guilty to having the dog uncontrolled and unmuzzled in a public place.

Magistrate Chris Bone said there had been a "moral failing" on the defendant's behalf because she had not disclosed the animal's dangerous dog status to the new owner.

"I think there has been a moral failing in not taking that letter or a copy of it with her when she spoke to [the new owner]," he said.

"I really think you should've. That wouldn't have been hard, that wouldn't have been difficult. You knew that there was a problem with Storm, although you may not have known all the ins and outs of it."

In reply the defendant said she had mentioned it to the new owner.

"He ticked the box on the changeover of registration sheet," she said. "I explained everything to him and he still took the dog."

Magistrate Bone fined Pearce $300 and imposed a 12 month disqualification from owning or being in charge of a dog in a public place. She received a section 10 for the other two charges.

Pearce will also have to pay the prosecution Queanbeyan City Council's legal costs totalling $5360.27.

A council spokesperson confirmed Storm had been euthanised by a vet a day after the attack on the teenager girl.