The CARS (302.11 (1); 602.06 and the Non Smokers Health Act prohibit smoking by passengers or crew on any Canadian registered aircraft, at all times.
Perhaps your aunt could make it over the pond the way smoking crew members do. They slap on a Nicoderm patch for the duration of the flight.
I'm a smoker myself and when my brother finally convinced me to visit him in England, I made sure I boarded the flight bone weary and I slept for most of the trip there and back.