Couzens killed Sarah Everard in south-west London days after exposing himself to staff at a branch of McDonalds.
Samantha Lee is accused of failing to make "the correct investigative inquiries" into the incidents and lying about her work on the case.
She denies gross misconduct.
A disciplinary hearing has heard that Ms Lee attended the restaurant in Swanley to interview the manager on 3 March, hours before Ms Everard was kidnapped and murdered by Couzens in Clapham.
She said afterwards she believed there was no CCTV footage of the incidents as the restaurant's footage had been deleted.
She previously told the hearing the meeting was her last appointment of the day before having some time off to rest.
On Wednesday, the hearing heard her written response made to claims she had breached standards, dated from June 2021.
In it she said Ch Supt Shepherd had called her during her days off and informed her she was still on the case, which "shocked" her.
"I could not believe that the crime report would be still shown to me, believing that it would have been transferred to MiST (My investigation Support Team)," she wrote.
She added that "had I known, or been aware, that it had not been transferred, I would have transferred it or spoken to a supervisor about it getting transferred".
Ch Supt Shepherd previously told the hearing he had not called her.
The hearing also heard that in an interview in November 2021 she said she had been "quite confident" she had done "what was needed" to have the case referred, and that it should have been cleared with a supervisor.
"After you complete an appointment, supervisors should then check your report and it should be passed onto MiST," she said.
Ms Lee is accused of breaching the force's standards on duties and responsibilities as well as honesty and integrity.
If she is found to have committed gross misconduct, she could be banned from serving in the force again.
In March this year, Couzens was sentenced to 19 months in prison after admitting indecent exposure.
He was already serving life behind bars for Ms Everard's kidnap and murder.
The misconduct hearing continues.