Yes, wait until after the PR is received to import/export, but that doesn't mean she can't drive the truck into Canada while she is visiting.
Be sure to declare it on the list of goods for landing including year, make, model, VIN number and "bluebook" value. Also, you will have to submit a copy of the title to the US customs office a couple days BEFORE you plan to export it. I assume you have already checked to see if the vehicle is admissible to Canada and know about all the steps to follow to get it registered, etc.