The sentencing guidelines for this offence depend on the category of harm and culpability.
It would appear from the description that this is the highest category which has a starting point of one year and a range of 26 weeks to 18 months with a maximum of two years.
According to the BBC she was sentenced on two counts consecutively, to two years and one year.
She pleaded not guilty at first and only changed her plea after the trial had started. I would guess that she was given no credit for that.
In contrast, if she had pleaded guilty at the first opportunity then there would have been a 33% reduction. So, if the judge had decided on the same sentence then, with the reduction, she would have been sentenced to two years.
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Another poster said that child sex offenders get less time in prison or even probation and I agree that this is wrong, but you need to look at the sentencing guidelines for those offences.
This woman shared, presumably, a photo of the OW "in an intimate state". It included substantial planning which was an aggravating factor. In contrast, the lowest category of this offence has a starting point of 12 weeks in prison with a range of a community order up to 26 weeks in prison.
The equivalent category of offence involving indecent images of children of the same type also has a starting point of 13 weeks and a range of a community order up to 26 weeks in prison.
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The big difference is that she was clearly at the highest level of culpability and harm and pleaded not guilty. That makes a huge difference.
The equivalent category for distributing indecent images offences has a starting point of 3 years and a range of 2 to 5 years in prison. But many, maybe most, will plead guilty at the first opportunity and so get a 33% reduction.