Once you're married she / you can apply for the spouse visa which would allow her to work wherever she once. Once she's in the country with the visa everything will pretty much be open to her (she'll be able to setup a bank account etc) and there will be no restrictions on her work. Citizenship comes much later for her.

Another route though may be available through her family. I'm assuming she's not completely Canadian (who is?) and her parents / grandparents may be from Europe. If so, she may be able to apply for citizenship through one of those countries based on ancestry. She could then work in the EU through an EU passport. However, it's pointless in the long run due to Brexit.

I doubt Brexit will effect you too much. Although the government have made it much harder to bring a spouse into the country these last few years, mostly by adding financial restrictions which it sounds like you can manage anyway. I wouldn't focus too much on the EU angle as it's redundant unless you're planning to move somewhere within the EU.