at that period a good chance cremated rather than buried - no Edith Dawson in burials (see www.iomfhs.im) - the other option is to look at newspapers (the IoM Times is often available via the BL newspaper digitisation scheme via larger public libraries) for death announcements
If Dawson was her maiden name can you not find her on 1911 census - might be able to restrict search - likewise the death cert should show age - again a newspaper search on BMDs might throw up something.