There is no prohibition against her applying for a TRV, but such applications are often simply viewed as being made by those who want to remain in Canada with their spouse, hence they will overstay. But, she might manage it if she can show very strong ties to draw her home, a good travel history, a job to which to return, property ownership, etc., etc.
We tried when my wife's PR application was 4 months along, with AOR, SA, PCCs submitted and medical exams all done, and I had been with her in her country for those four months. It took all of 2 days to get a denial. But, your case might be different.