Mrs Schaar came into the kitchen and Ms Spence asked why she was being sent home. She started walking towards Mrs Schaar, who put both her hands out and pushed her backwards.
Mrs Schaar claimed she did this because she was afraid Ms Spence was going to assault her.
In response, Ms Spence said she reacted by pushing back but Mrs Schaar and her husband Pieter claimed Ms Spence punched Mrs Schaar on the shoulder.
Police were called and Ms Spence never returned to work.
A police spokesman said no charges were laid over the incident but said Mrs Schaar was within her rights to escort Ms Spence from the property.
ERA member Christine Hickey determined the decision to send Ms Spence home amounted to a summary dismissal because, although she was on notice that her job was to end, this was not to happen until the end of the month.
She did not accept Mrs Schaar's perception that Ms Spence was going to assault her excused her from instigating "hostile physical conduct".
"In the absence of justification such as self defence, a physical assault on an employee by an employer must always be an unfair action," she said.
Ms Spence told the ERA that her son came home from school after the incident and said that Mrs Schaar's daughter had told their class that Ms Spence had hit her mother.
She said she was "so humiliated I could not go to school to pick our child up", the ERA decision said.
Lake Ohau Holdings Ltd was ordered to pay Ms Spence $7500 compensation.
Ms Spence could not be reached for comment and Mrs Schaar declined to comment.