I grabbed a few page captures of the Campbell families in volume 1, but didn't find a likely one for an 1833 birth en route to Ontario. What did the MyHeritage citation say?
There's a MyHeritage tree that has Flora as daughter of "William Campbell and Isabella Campbell (born Mason). Isabella was born in 1765." But there's no William Campbell in volume 1 of the Lawson book.
If those parents are right this could be their marriage, but Elgin is nowhere near the Western Isles. I like this because there are two children of William and Isabella living in Hastings, Ontario, and they are both born just before 1833 and both born in Scotland.
"Scotland Marriages, 1561-1910," database, FamilySearch(https://familysearch.org/ark:/61903/1:1:XYSX-H4V : 10 February 2018), William Campbell and Isobel Masson, 01 Dec 1827; citing Elgin, Moray, Scotland, index based upon data collected by the Genealogical Society of Utah, Salt Lake City; FHL microfilm 990,801.