Police criticised over death.
Casey Brittle, 21, repeatedly called Nottinghamshire Police before she was murdered by Sanchez Williams.
Amerdeep Somal, a commissioner at the Independent Police Complaints Commission (IPCC), said Williams, from Nottingham, was "well-known to local police for his propensity for violence and threatening behaviour".
"In this case it is clear that a number of officers failed to perform to the level expected of them and basic actions, that may have helped others see the full picture of her suffering, were not completed," the commissioner said.
"No consideration was given to why Casey was reporting domestic abuse but then subsequently saying that she did not want police help."