Thanks All for your reply
I would like to make some clarifications
1. We are NOT yet married (and also not formally engaged sos no engagement photos, but we have LOTS of photos we have taken together, dating like 4yrs back!) and so she is not yet my spouse
2. We are both not canadian citizens ( I am here in canada as a graduate student)
3. If I state in the letter of invite that I want her to come here so that we could marry, wouldnt that affect the visa
4. She currently works for a multinational company in the UK (so vedry much employed and would be willing to return after the marriage)
So I request steps on what we need to do to secure her a visitor visa with nO hasssles