Marketing executive Ms Everard, 33, went missing as she walked home from a friend’s house in Clapham, south London, on March 3.
She was reported missing by her boyfriend on March 4 and her body was found hidden in an area of woodland in Ashford, Kent on March 10.
The woman, in her 30s, was arrested on March 9 on suspicion of assisting an offender and was bailed until early June.
Police said today she has been “released with no further action” being taken.
Watch: Wayne Couzens admits killing Sarah Everard; plus Keir Starmer's popularity plummets
The woman was arrested at the same time as PC Wayne Couzens.
The 48-year-old appeared at the Old Bailey on Tuesday, when he pleaded guilty to the kidnap and rape of Sarah Everard.
Couzens was not asked to enter a plea to a charge of murder between March 2 and 10.
The court heard that responsibility for the killing was admitted but medical reports were awaited.
Members of Ms Everard’s family sat in court to witness the defendant enter his pleas.
A further hearing before Lord Justice Fulford is due to take place on July 9.
Couzens, from Deal in Kent, sat hunched over in a chair with his head bowed throughout the hearing.
The Metropolitan Police officer was wearing khaki trousers and a grey sweatshirt as he appeared by video link from Belmarsh jail.
Watch: Sarah Everard died from compression of neck, post-mortem finds