"I still can't get my head round the fact that she's been sent to prison for a theoretical crime"
??? She committed an actual crime, which she confessed to.
"The defendant pleaded guilty in July to administering a poison with intent to procure a miscarriage.
She told a psychiatrist she had taken the drug while her husband was away and delivered the baby boy by herself at home."
That carries a potential life sentence.
If you plead guilty to a serious crime, then there's nothing more to say, and certainly nothing theoretical about it....
Of course she was guilty in any case of acquiring the drug, a crime in itself, but she went on to confess to taking it, so it's cut and dried really.