In 1851 the family are in Kensington;
Henry aged 37 born Stratton, Glouc.
Maria aged 51 b Norfolk
George 4 b Kensington
Harry 1 b Kensington
If she had been previously married both former names should be shown BUT may not have been. She would have married with her 'married' name. That was my first thought in view of the age difference - although from the census in 1851 - it's 14 years and not 20 years difference.