A young solo mother has pleaded guilty to sexually exploiting a 14-year-old girl.

Monika Rachael Kelly, 19, appeared today in the High Court at Auckland where she admitted to dealing in people under 18 for sexual exploitation.

It is one of several such cases to be heard in New Zealand's courts this year.

Kelly will be sentenced later this year.

Justice Mathew Downs told Kelly: "There is every prospect I will send you to prison, I have not made my mind up."

He said such offending can lead to a lengthy prison term.

Kelly was operating an illegitimate prostitution service using a 14-year-old girl, court documents obtained by the Herald show.

Business for the service was made by Kelly seeking men on a smartphone using an application called "seeking arrangements", which was similar to a dating website.

Kelly made a profile for the teenage victim using an alias for the girl and amended her date of birth to be 18 or 19 years of age.

Four times the teen was exploited in this way at central Auckland hotels with Kelly receiving payments of up to $350.

A police investigation began in mid-July last year.

After Kelly learned of police involvement she arranged for her associates who had witnessed the offending to meet.

She collectively advised at least two of them to tell police they had no knowledge of the circumstances of the offending and provided them with a prompt of what to say.

When spoken to by police, Kelly admitted to driving the teen to the clients and receiving payment, however, she denied making the arrangements and said she was only trying to help her victim out.

Earlier this month, the Herald revealed police were alerted to a couple pimping out a 15-year-old after the girl's mum discovered on social media her daughter had been flown from Christchurch to work in central Auckland brothels.

Taton Sebastian Smith, 35, and Tahleicia Elizabeth Seil, 25, were sentenced for assisting someone under 18 to provide sexual services.

Smith was jailed for two years and 10 months, while Seil will serve nine months' home detention after they had earlier pleaded guilty.

Both also were also sentenced for profiting from the activity, and Smith for having sex with a person aged 12 to 16.

Earlier this year, the Herald also revealed one of New Zealand's most sickening criminal cases and just the third conviction for slave trading in the country's legal history.

Kasmeer Lata was jailed for six years and 11 months in April for keeping her daughter as a sex slave, turning her Auckland home into a brothel, and selling the 15-year-old to men some 1000 times over a two-year period.

Justice Matthew Muir said at Lata's sentencing: "New Zealand's courts will not [tolerate] the prostitution of children."

Her partner, Avneensh Sehgal, who attempted to flee to India, was also imprisoned.

And last month, the Herald reported on a Lower Hutt woman who planned to sexually exploit her 10-year-old granddaughter to sex criminal Andrew Davie.

Davie was jailed for three years and five months, while the grandma was sentenced to three years and three months in prison.