A mother who admitted she slapped her 10-year-old daughter about the face and body at least five times to discipline her for back-chatting has been given nine months' supervision.

Isobel Hine Crown, 43, was found guilty of one charge of assault on a child by Judge Thomas Ingram after a defended hearing in the Tauranga District Court.

The judge told her she went well beyond what was deemed reasonable force to discipline her child.

As part of her sentence, Crown must undertake any courses and counselling to address the causes of her offending, as directed by her probation officer, including counselling to remedy her drinking problem.

Constable Robert Everitt of Te Puke police said that at 5.40pm on February 15 he went to a property in Paengaroa in the western Bay of Plenty after a 111 call from Crown's daughter.

The girl was calling from a house across the road from her home.

The distraught girl, whose face was red down one side, said she had been slapped about the face and body about 10 times by her mother.

She said her mother had become angry with her while she was trying to help change a 1-year-old's nappy.

"She was very upset, shaking and crying the whole time I was talking to her. She told me she was scared and called the police because she didn't know what else to do," Mr Everitt said.

While he was still speaking to the girl, her mother turned up.

She was very intoxicated, yelled abuse and was swearing at her daughter, repeatedly calling her "a little bitch" and saying, "Look at the trouble you have caused".

Crown admitted she had slapped her daughter's face and body about three times. She had done so because her daughter had sworn at her and got smart with her when she tried to correct her, Mr Everitt said. Crown also admitted she had started drinking around 8am, he said.

Crown's lawyer, John Holmes, argued there was no case to answer because there were no independent witnesses to corroborate the daughter's allegation against her mother.

But Judge Ingram disagreed. "Clearly there is a case to answer here, particularly after Miss Crown's own admission to police that she slapped her daughter, and then there is the victim impact statement."

Crown claimed she slapped her daughter because she had hit her 1-year-old grandchild.

According to Crown the baby was screaming and struggling during a nappy change. She said her daughter got angry and slapped the child on the legs and thighs several times.

Asked in court by Mr Holmes if she considered her actions as her exercising parental discipline, Crown replied: "Sort of. But it's the first time I have hit her in this way. I was pissed off. There was no need for her to slap the baby."