Judy's Death — Gillian Larkin

Cara Daniels has a secret job. She saves the lives of people who are going to be murdered. She also saves the souls of the people who are due to commit the murder.
In book 2, Cara meets the angel who is going to help her stop a murder from going ahead. The murder victim is Judy Wallace. Judy works at the local library and is going to be murdered in less than 48 hours.
As the investigation begins, Cara is not sure if her angel is going to be a help or a hindrance.