Miss Moore (19) beat seven contenders to win by a 122-vote majority when results were announced two weeks ago.
After investigating two complaints against her, returning officer Kyle Matthews said yesterday the single breach he found was "only moderate" and the election result should stand.
The complainants have five working days to lodge an appeal, but Miss Moore said yesterday she did not believe that would happen.
"I'm happy it's all over. I'm very confident it is."
However, she said if an appeal was lodged she would "fight it, all guns firing".
"I have some very good lawyers behind me if I need them."
After investigating the complaints, Mr Matthews said some of the issues raised were found to be inaccurate, "most likely as the result of rumour".
"But I have also found that the candidate did breach an OUSA elections rule by placing a number of posters and advertising materials on private property.
"I have, however, ruled that this was only a moderate breach and does not place the outcome of the election in doubt."
Miss Moore was also accused of breaching an OUSA rule by campaigning within 20m of a polling booth.
Mr Matthews ruled she had not breached the rule, but recommended the OUSA executive review the rule for future elections.
She "ran an active campaign and, at times, did step over the line set by the rules", Mr Matthews said.
"However, she also engaged the student body and was a convincing winner ahead of the second-placed candidate.
"I have no doubt that it was this engagement, not any breaches of the rules, which led to her victory."
