Hello,
In the 1911 Canadian Census I found Anthony Doiron living in St. Mary's township 23 Queens County, P.E.I., born Jan 1848 married to Phemi Gallant born June 1858. Their children: Margaret born Jan 1886, Angelina Feb, 1895 Emily Jan 1898 and Anthony July 1891
Could this be your Margaret's family? Anthime may have changed his name to Anthony and Philomen could have been called Phemi. This census gives the maiden names of the wives, something I never noticed before and indeed Phemi's maiden name is Gallant.
If this is your Margaret Doiron who married Joseph Isidore Gallant they have to have married after 1911. Unfortunately Canada has not made any censuses public after the 1911 census.