Thanks all for the input, really appreciate the help. I've put together all the information given and her history I have found below to try to hopefully help solve the mystery although I think it will take some time to find what happened to her.
1880 10th November born Elm, Cambridgeshire
1881 Friday Bridge, Elm, Cambridgeshire on census 5 months old
1882 Death of Mother Isabella Denton
1891 Friday Bridge, 2, Barracks, Friday Bridge, Elm, Cambridgeshire on census
1901 23, Gathorne Terrace, Potter Newton, Leeds - Servant
1901 Esther Foster single with 1 child living with widowed mother at 66 John St.
1905 Death of brother Francis John Bates and sister Emma Jane Bates
1911 Esther Foster boarder with 2 children living at 78 Church Street
1913 26th September - 406, Hitchin Road, Luton. Leslie Spalding Bates born.
1913 6th November - 333, High Town Road, Luton residence when registered.
1913 6th November - occupation - Theatre attendant when Leslie registered
1915 2nd June - 16, Park place, Park Street,Luton. Albert Spalding Kitchener Bates born
1915 12th July - occupation - Domestic servant when Albert birth registered
1915 - 7 Park Lane -Esther Foster
1916 - 16, Park place, Park Street,Luton - Mrs Bates
1916 - 7 Park Lane -Esther Foster
1917 - 16, Park place, Park Street,Luton - Mrs Bates
1917 - 7 Park Lane -Esther Foster
1918 - 16, Park place, Park Street,Luton - Mrs Bates
1918 - 7 Park Lane -Esther Foster
1919 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1920 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1921 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1922 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1923 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1924 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1925 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1926 - 7 Park Lane - Ada Bates, Emma Burton and Esther Foster
1932 - Death of Father Thomas Bates
1939 - Esther Foster as widow at 23 Bury Park Road, Luton