Horsley's humanitarian values led her to treat some patients free of charge, and sometimes donate money to patients. She also took on unmarried mothers as domestic help. Horsley served as an anaesthetist in the Military Hospital during WWI. Horsley worked throughout the plague scare of 1900 and the 1918 influenza epidemic, and was a member of the medical relief team after the Hawke's Bay earthquake of 1931, in which hundreds were killed and thousands injured.