You will have to find out just when she came to Canada. The best place to check for this is the Archives of Canada. If you can find her arrival date on the microfilm and if you are in Canada just take the film number and any other information that is given to your local library and they can order it in for you to view. It should tell you what part of England she came from. Another suggestion is to call your local Church of the Latter Day Saints (Mormons) and find out if they have research facilities. They may be able to help you.
I did a quick search of passenger records leaving England between 1920 and 1939 on the FindMyPast web site and could not find an Edith Cheetham of the right age give or take 3 years. These were ships records.