can you find Sarah 1841?

[Nell]

Sarah Marsden b 1796 Colchester, Essex
married James Muir 1817 St. Giles Cripplegate, City of London

I don't know if they had any children.

1844 Sarah Muir, widow, married Henry Banister at St. John the Baptist, Hoxton and I have her in 1851 with Henry living 4 White Lion Yard, St Luke Old Street, Middlesex and 1861 8 Glouster [sic] Court, Whitecross Street, Finsbury, Middlesex before her likely death 1866.

So theoretically she should be in London in 1841 as Sarah Muir but I can't find her.

Help!