The investigator found the lecturer had breached the university's conflict of interest statute "at the lower end of the scale" when he failed to disclose their intimate or domestic relationship, which began after he had marked her paper for the course.
It was deemed a low-level breach because it did not affect the student's mark for the course.
The student's other allegations, including of physical assault, were not substantiated.
She had claimed that during a university trip in January, they stayed together at the lecturer's accommodation where he physically assaulted her, which resulted in bruising multiple parts of her body.
"On the balance of probabilities, the investigator found there was no evidence to suggest that your injuries were sustained from an assault by the staff member as opposed to the staff member and the other individual attempting to restrain you," the letter said.
"He noted that your view was that you did not lay charges with the police due to your concern about how it would impact you financially and also your concern about whether it would impact your visa renewal.
"Irrespective of the reasons, the investigator noted that no charges were laid."
The lecturer's trip was funded by another university and the student paid for her own ticket.
Bryson said in the letter that the university has "addressed the matter of the established low-level breach of university policy" with the staff member and taken appropriate action.
"The details of that action are a private employment matter between the staff member and the university, which I am unable to disclose," she said.
Bryson said steps have been taken to ensure the staff member and the student will not have further contact with each other in relation to any university academic matters.
'After giving careful consideration to the report, I advise that it was my decision to accept the findings of the investigator in full," she said.
A university spokeswoman said it will not make any further comment on this matter "given the sensitivity of the situation and out of respect for the privacy and wellbeing of the people allegedly involved, and to prevent the spread of possible misinformation".