I will echo what
@scylla has already stated. A person with a DUI conviction, where 10 years have not passed since the completion of their sentence, are in fact inadmissible. If they are not `detected' when entering Canada, that's really a potential flaw in the system, but having said that, perhaps it's a Secondary Inspection that would have found the DUI in the case of the OP's wife. To digress, IRCC also says that a PR must have a valid PR card to
enter Canada via a commercial carrier, which is not true. A PR with a valid U.S. passport can travel on that alone (to board a plane). All other PR holders must have a valid card to appease the carrier. This has NOTHING to do with `entering' Canada, since the `entering' part comes well after a passenger has exited the aircraft.
When I suggested `laying low', that was merely that; a suggestion "...she should consider...". If the OP's wife is stopped (for whatever reason) and is asked to produce their DL, it is certainly possible that the DUI would show up if/when the officer runs it through the system and if questioned about it, could only add to their angst. But again...it was only a suggestion.
It would seem logical that the visa officer working on the application has deduced that 10 years have NOT passed since the completion of the sentence and, at least at this point, would have the right to refuse the application. The OP cannot dispute that fact.
I, like everyone else here I'm sure, hope that the application is ultimately approved.