She is to undergo surgery on Monday after falling ill.
Her partner, fellow lawyer Rupert Glover, appeared at an unscheduled hearing in the High Court at Christchurch today to inform Justice Warwick Gendall of the enforced delay.
The case will next be called on August 16 for a pre-trial callover when a firm trial date will be set, likely to be later in the year.
The defendant remains in custody.
Ms Sewell appeared for double teen killer Jeremy McLaughlin when he was convicted in the High Court at Christchurch earlier this year for the murder of city schoolgirl Jade Bayliss.