Hi! My own experience and my research shows that once you have a marriage certificate, nobody will ask you anything! If you don't have a marriage certificate, than you have explaining to do.
If you are a Canadian resident, and she can manage to come to Canada even for a visit, you could get married in Canada during her stay, and that would probably be the best. However, it sounds that they are refusing to give her VISA? Have you tried getting her a tourist VISA? If you could get one of your relatives/friends to write her an invitation letter, guaranteeing that they will take care of her during her stay, and explaining their relationship, that might work. My uncle, who lives in Canada, did that to get our cousins to visit to Canada, and I did the same, while living in the USA, to get our cousins to visit in USA.
If you in fact can get married in Argentina, (considering that neither of you is Argentinian citizen, and since most countries that allow same-sex marriage do require that at least one person is from that country), you should get married there!
The application to come to Canada only asks for marriage certificate (with proper translation and apostle), and nothing else. If they happen to call you for an interview, than you can bring all your photos and other evidence. Once your are both in Canada, you can always get married again, with family and everything else you wanted for a wedding
When my spouse applied for her open-work-visa (which includes temporary residence), all she submitted online is: scan of her passport, scan of my passport and my Canadian work visa, scan of our marriage certificate from Mexico city, including a translation and apostle, and one form, and that's it.
good luck!