Cumming said her "erratic" supervision and other factors, including her partner's dismissal by the company, had caused her stress and led to the outburst.
Immediate after management called at which Cumming had no support person.
At a second meeting she grudgingly apologised to Boon, but warned of further reaction if her supervisor "got in her face again", said the ruling.
Cumming was then dismissed after director Craig Hudgell said "the threat of violence outweighed all other considerations".
Absolute management acknowledged the dismissal was unjustified.
The authority ordered the company to pay Cumming $5000 and reimburse her filing fee of $71.55.