Well, yes and no. They did the best they could, but most airplanes then did not have the range to fly a true great circle (polar) route from London to Calgary, Vancouver or Seattle. Thus they would have an intermediate stop in Gander Newfoundland to refuel, take on more food and drink, and empty the wastewater holding tanks.
I must’ve missed something. Why are people assuming that a direct flight from London to Vancouver existed back in 1961, especially if that flight had to stop and refuel in Nowheresville, Newfoundland? If she was going from London to Seattle, wouldn’t it be more likely that there was a transfer (or 2 or 3)? Based on the Harvard connection, I’d assume Logan (if that was open in 1961). If not that, NYC.