A West Coast woman convicted of having a sexual relationship with a 14-year-old boy has been jailed for three years.

The woman, now 33, was sentenced in the Greymouth District Court on Friday following her conviction on 11 charges.

In jailing the woman, Judge Stephen O'Driscoll granted a further interim name suppression order until 10am tomorrow, when she can be named.

She was 28 at the time of the offending and the victim was 13 when he came to live with her.

Judge O'Driscoll noted that the woman had been convicted on 11 charges, eight of unlawful sexual connection with a young person and three of doing an indecent act, but some of these were representative, with the offending taking place over a period when the boy was aged about 14.

The main purpose of the jail sentence was "deterrence", the judge said.

While the offender had been assessed as being at low risk of re-offending, the judge said he had to keep in mind the need for "general deterrence, that this type of behaviour will not be tolerated".

"The whole purpose of the law is designed to protect vulnerable young people," Judge O'Driscoll said.

The woman "should have stepped back" when things became sexual. Her offending was serious, grave and highly culpable.

The judge noted he could not reduce the sentence starting point just because the offender was a female and the victim a male.

"Gender is irrelevant. As I have said previously, the absence of an aggravating factor is not a mitigating factor.

"The sad reality with your offending is that many others suffer ... it's not just a matter of the offending affecting only the victim."

She had "overstepped the boundaries" between adults and children.

"It is clear this happened within a relatively short time of him arriving at your address," Judge O'Driscoll said.

During the judge-alone trial in Greymouth, the woman had challenged the complainant, "that the offending did not take place".

"I note in the pre-sentence report that you continue to deny the offending and indicated that you intend to appeal," the judge said.

However, he noted there was other evidence from within the community of "an unhealthy relationship" between her and the boy.

The boy was 13 and from a "troubled background" when he first came to live with the woman.

"It is clear from the evidence I heard that you very quickly developed a close relationship with the victim."

This included a range of sexual activity including sexual intercourse.

A victim impact report noted the damage to the boy including important relationships which had left him with a "deep fear of new people".

While the boy might have been physically bigger than the woman, despite his young age at the time, that was irrelevant, the judge said.

"I have no doubt from seeing him give evidence that he was physically mature, notwithstanding his young age."

The victim was "an emotionally immature and insecure boy".

"It is clear your relationship with him has had a significant detrimental effect on him. You have continued to deny the offending," the judge told the woman.

While the woman had no previous convictions, aggravating factors were the age difference and the breach of trust.

The Crown had submitted "an element of grooming" by the offender, although the judge said he was satisfied that had not happened.