MJH would not comment on the dismissal, but when approached gave the following statement.
"The company strongly condemns bullying and violence of any sort in the workplace and has a robust range of policies and procedures in place to prohibit these types of behaviours and to assist staff who may have been impacted by them," it said.
"The highest levels of conduct and professionalism are also expected from our employees."
A company spokeswoman said the matter was currently the subject of an ongoing police investigation and it will assist the police in their investigation as required.
According to the dismissal letter, the staff member failed to attend a formal meeting to give her response to concerns raised during the disciplinary process.
The letter alleged that the sacked employee had also been "violent and disorderly" towards her colleague, whom she also swore at.
The manager also said that he deemed the trust between employee and employer "which is fundamental to the employment relationship" has been irreparably damaged by her actions.
Lawyer Erin Davies, head of law firm Meredith Connell's employment team, said employers can dismiss employees for speaking to media in certain circumstances.
"The Employment Relations Authority and Employment Court have found employees to be in breach of their employment agreements and/or duty of good faith and fidelity, resulting in a justifiable dismissal," she said.
Davies said employees have a few different ways of dealing with workplace issues, including serious matters such as a workplace assault.
These included raising an employment relationship problem with their employer, making a police complaint and notifying WorkSafe.
The staff had been warned against speaking to the media by her manager, who said in an earlier email that the company considered matters relating to the alleged assault as confidential.
"For the avoidance of doubt, MHJ [Michael Hill Jeweller] considers that any disclosure of such confidential information to media outlets would be deemed to be a breach of confidentiality, your individual employment agreement and MHJ's confidentiality policy," the manager wrote in that email.
Police confirmed it received a complaint relating to a minor assault incident between two parties at the store on February 8 and inquiries into the incident were ongoing.