A WOMAN who pleaded guilty to sex with the 16-year-old son of her partner will spend at least six months in jail, themercury.com.au reported.

Justice David Porter sentenced the 28-year-old, who cannot be named for legal reasons, in the Supreme Court in Hobart this afternoon.

He handed down a 12-month sentence backdated to May 20, with six months suspended on the condition she commit no offence for two years.

The online news article reported the court heard the woman had continued Facebook messaging with the boy from February this year until May 11, with the woman using a false name.

"You must bear full responsibility for what happened," Justice David Porter said.

"The relationship that commenced was more opportunistic than predatory ... but that cannot truly be said of your later conduct," Justice Porter told the woman in the dock.

"This calls for a lengthy sentence ... but there is sufficient prospect of rehabilitation."

The woman cried on realising she would be imprisoned.

Her lawyer Steven Chopping told the court she had been terrified by her short time in jail so far.

The court heard the woman had also attempted reconciliation with her former partner, with whom she had an 18-month-old child.

The court heard last week that the woman's partner had seen evidence of their affair after he set up a video he said was to capture paranormal activity.

The woman had pleaded guilty to seven counts of unlawful sex with a young person aged under 17.

Justice Porter said he took into account the woman's early plea of guilty.

But he said she continued the affair -- driving a distance to be with the boy -- despite being told by police she would be charged.

He said she had said she did not know the age of consent in Tasmania was 17, but did know this when she continued the relationship later.

More in tomorrow's Mercury.