Unfortunately, one can't count on anything these days when dealing with airlines. But keep all of your receipts and submit them with a complaint to WestJet, and/or a complaint to the Canadian authorities. Was your girlfriend required to overnight at Calgary to get a flight to Paris the next day? If so, she might be entitled to food and lodging reimbursement. Check the Canadian Airline Passenger regulations to which I linked in a prior post.

Good luck!

Edited to add: Whom did your girlfriend actually approach in the Paris airport? WestJet? Air France? LOT? Only the airline which operated the flight from Saskatoon to Calgary has the obligation to re-route the passenger to Warsaw.