In 2018, Simpson and her partner, Anthony Smith, were sentenced to 10 years in prison for the abuse of Tony Hudgell.
Simpson was scheduled for release on licence in August 2021 but Raab had referred her case to the Parole Board to delay her release.
However, that intervention was challenged in the High Court by Simpson and, in December, the judge ruled that Raab's referral of the case to the Board was unlawful and that Simpson's release could not be delayed any further.
Ms Hudgell, Tony's adoptive mother, expressed her shock at the news, saying that all they could do was now prepare Tony.
Ms Hudgell has previously campaigned for longer sentences for abusers.