Grace Batchoun was the runner-up to Joly, a lawyer and former Montreal mayoral candidate, in the hotly contested nomination in Ahuntsic-Cartierville.
Joly won Sunday on a third ballot by a margin of 194 votes.
In a formal appeal filed with the party, Batchoun says there were irregularities with the results.
She claims 2,065 ballots were counted, but only 1,780 people showed up to vote — a discrepancy of 285 votes.
The party says an appeal is not guaranteed to be heard and Joly remains the candidate.
Joly, an organizer on Trudeau's leadership campaign, was the party's preferred choice in the riding.
Her arrival on the scene created strife as fellow candidates had been in the running for several months.
Some of them accused the party of bending the rules surrounding the open nomination process to favour Joly, an allegation that has been steadfastly denied by the party.
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