So far there have been 3 Catherine Burnett's in the tree I have researched.

Catherine Edith Burnett born 9th October 1848 in St Martin District, Liverpool could be who your G Grandfather married. The family moved about around Scotland as her dad ran several Lighthouses before retiring on the IOM. Her mother nee Catherine Sayle was born in IOM c1821. Her father James Burnett born c1818 in Scotland. Was your census return for your Catherine E. Burnett listed as a Dressmaker by any chance? Great name for a place on IOM by the way....I had to look it up!!!