A young woman has pleaded guilty to the sexual exploitation of a child at the High Court in Auckland (file photo).

A young woman used a smartphone app to prostitute a 14-year-old girl, arranging for her to participate in group sex and an oil massage, then collecting payment.

Nineteen-year-old Monika Kelly, a single mother, appeared in the High Court at Auckland on Friday, where she pleaded guilty to one charge of the sexual exploitation of a 14-year-old girl.

Between March 18, 2017 and April 26, 2017 Kelly entered into dealings of a person under 18 for the purposes of sexual exploitation, court documents showed.

The police summary of facts stated Kelly set up a profile for the victim, using an alias, on the smartphone app 'Seeking Arrangements'.

She changed the victim's date of birth to make it appear as if she was 18 or 19 years old.

On March 19, 2017, Kelly began communicating with a man, and an arrangement was made to deliver the victim to an office building in the CBD to perform sexual acts, the documents showed.

Kelly took the victim to the office building, where the victim had sexual intercourse and an oil massage with the man.

Kelly then received payment and provided part of the money to the victim, the documents showed.

Two weeks later, on April 4, Kelly and the man negotiated for the victim to go to Auckland's City Life Hotel for group sex.

"On this day, it was initially agreed by the defendant and the male that additional men would be involved in the intercourse with Complainant A and that she would remain with the male and his associates for a period of 90 minutes at a price of $350," the summary of facts said.

Although the arrangement was for group sex, only one man was present, the documents said.

Again, Kelly received payment for this.

On April 11, arrangements were made for the victim to go to the Best Western President Hotel for a "quickie", and for the man involved to film the act and pay $200.

It was not known whether any filming took place.

On Anzac Day, Kelly transported the victim to City Life Hotel, where she had sex with a man for $350 while Kelly waited outside, the summary of facts said.

After learning about a police investigation into her actions, in July 2017, Kelly arranged to meet up with a number of associates who had witnessed the offending to try and prevent them from providing evidence, the documents showed.

Kelly admitted to police she drove the victim and received payments, however she said she did not make the arrangements and was only trying to help the victim out.

On Friday, Kelly's lawyer Ron Mansfield said his client had no previous convictions when originally charged, however now had minor convictions for shoplifting.

Kelly was set to face a judge-alone trial on Monday at the High Court.

Justice Mathew Downs told Kelly she would be sentenced on November 13, and "a term of imprisonment is likely".