Restore — Susan Kaye Quinn

Restorative Human Medical Care Unit 7435, sentience level fifty, is happiness level five out of ten to serve and heal the human master it loves. But Unit 7435 finds there is a price to be paid for love... and for failing in its primary mission.  Restore  is a standalone short story that takes place in the world of the Singularity novels.  Start the novel series with The Legacy Human (Singularity 1).