A Perth woman has been jailed for physically, verbally and emotionally abusing a four-year-old girl who she kicked, smothered with a pillow, pulled by the hair and slapped in the face.

Katherine Ellen Walker, 26, admitted committing the offences while she and her partner were looking after the child on a two-week holiday in Western Australia's South West.

The District Court was told the abuse happened on five separate occasions, and some of it was recorded by the partner on her mobile phone to try to stop the violence.

Walker pleaded guilty to a charge of having care of a child and knowingly engaging in conduct that may result in physical, emotional and psychological harm, as well as five counts of aggravated common assault.

State prosecutor Michael Cvetkovski said in one of the incidents, Walker held a pillow over the child's face and told her "I want to smother you until you die", before asking "can you breathe, can you breathe?" and calling her a "stupid c**t".

"Go to sleep before I come in here and pummel you until you die," she also told the child.

On another occasion, Walker verbally abused the child for not being able to wash herself properly in the shower, before lifting her off the ground by her hair and dropping her onto the tiled floor.

As the child lay crying, Walker used her foot to push her across the floor, causing the girl to hit the wall.

The court heard the child was then taken to a bedroom where she was rolled off the bed's mattress onto the floor and repeatedly kicked in the back.

Walker also poked her, squeezed her nose and hit her on the legs and stomach.

Mr Cvetkovski said there was also an incident in which Walker grabbed the girl by the hair and poured chilli sauce into her mouth.

Suicide pact with partner

Walker's lawyer Paul Sullivan said his client could not recall any of the assaults because she was under the influence of oxycodone, which she had become addicted to after being prescribed it for endometriosis.

The court heard after Walker was charged, she and her partner entered into a suicide pact to take an overdose of drugs — but Walker awoke and was seen on CCTV stumbling out of the apartment where they were staying before going home.

Walker will need to serve at least half of her three-and-a-half year jail sentence. ( Facebook: Katherine Walker )

Her girlfriend died.

Judge Laurie Levy said he found some of the circumstances of that story "troubling" and "difficult to reconcile", particularly that Walker made no attempt to check on her partner's condition.

But Mr Cvetovski said the matter had been investigated by police and no further action was going to be taken.

Judge Levy said only an immediate jail term was appropriate for the offences committed against the child, saying the language Walker had used was "appalling" and there was "something like 33 separate acts of violence", including punching, kicking, slapping, dragging, smothering and pulling by the hair.

Judge Levy said he accepted that Walker's judgement at the time of the assaults on the child may have been impaired by her drug use, but he said she had voluntarily taken the oxycodone.

He said the offences were "extremely serious examples" of aggravated common assault, and it was difficult to think of much more serious offences committed against a young child.

Judge Levy sentenced Walker will to three-and-a-half years in jail, and she will have to serve half the term before she can be released.