Slavery: Was My Mother A Slave In All But Name?

Back in E. Yorkshire in the 1930s, my Mum was 'in service' at a big house. She worked six very long days a week and was paid three shillings and sixpence. (17.5p) Her 'keep' was part of the deal. So, just 17 and a half pence away from being classed as a slave?