Your worries are completely understandable. I just went through what you will soon. My wife came here a couple of weeks ago, and instead of it being a happy day of reunion, I was a nervous wreck at the airport. Days before, and even at the airport, I was worried sick with thoughts like "what if she's refused entry?", "what if they interrogate her and tell her they don't believe she's only visiting?', "what if they tell her she's lying and going to defraud Canada?", "what if they don't let her in and put her on a return flight? I'll be devastated! Our lives will be ruined" :'(
You know what, though? She breezed through Customs and immigration, they didn't ask her a single thing, they didn't even inspect suitcases, much less interrogate her. So, while your worries are understandable, they're extreme
Immigration Canada and the CBSA are staffed by good people. In the end, these people are also family people and they're not out there to destroy families and couples for no good reason. They're reasonable and humane with their heart in the right place. What you should understand is that they have a job to do, and that travelers that try to enter Canada shouldn't make their job difficult.
Will your wife be coming to visit as a tourist, declaring (if asked) that she intends to leave Canada with her return ticket? Yes.
Do the agents know that chances are she will stay and apply inland? Yes, they know the statistics and are not stupid.
BUT, as long as you give them the benefit of doubt, "My intention is to visit. Have I considered staying?
(if asked) Sure, but it's only a possibility, not a certainty," as long as you can honestly tell them that (and as I previously said, it should be the honest truth because nothing in life is certain and such a decision should be finalized here), you will keep their job easy. They will appreciate it and be able to justify letting her in. They will appreciate her, for her honesty, for keeping their job easy, and for being smart about it all.
So, keep a possibility of return in your minds, even if it seemed unlikely and unpleasant until now. That possibility will enable immigration officers to allow entry. If her responses to any questions are reassuring and not worrying ("I'm only visiting, I have family back home I stay with, etc etc"), there won't be a problem.
Above all, don't worry! You will pick her up from the airport, go back to your place together and you'll be the happiest guy in Canada that day