I have now received a letter back from the medical officer. Sarah was admitted in 1909 with the reason as pregnancy and she stayed there until her death in 1933.

I am now having trouble with the fact that the 1901 and 1911 census state that she was born in 1876 but the 1881 census has Sarah as being born in 1866 which is 10 years difference. Her parents are defintely Thomas Davis (1825-1912) and Margaret (1841) and this is what the census in 1881 states but with a difference of 10 years in Sarah's birth date.