his addiction to tobacco, which killed him at the tender age of 55.
Elizabeth Bowes-Lyon must have suffered terribly, seeing her husband smoke THIRTY to FORTY cigarettes a day, plus several pipes and cigars.
God is subtle, but He is not malicious. (Albert Einstein)
Although plenty of doctors condemned tobacco usage as a filthy habit, the definitive link between smoking and lung cancer had not been established by the time George VI died. For years Elizabeth (the Queen Mum) blamed his early death on the stress of his being a wartime king, not on his smoking.
Curiously, Elizabeth lived to be almost 102. She must have been immune to secondhand smoke.
According to smokefree.gov, lung function starts to improve within three months after one stops smoking. So, if Elizabeth never smoked at all (and I've never seen her portrayed as smoking, so that premise is entirely possible), the dangers exposed to her via secondhand smoke would have decreased dramatically within a year of George's death.
Princess Margaret also smoked, but most likely Elizabeth would not have been as exposed to her daughter's cigarettes as she was to her husband's.
Or, she could have just been lucky. Some people are. It's part of what makes cancer such a crapshoot.