Ms Dornan was stabbed at her home in the Lagmore estate which was set on fire on August 2, last year.
The PPS said it had begun extradition proceedings to return Raymond O’Neill to Northern Ireland for prosecution.
O’Neill was arrested by police in the Republic of Ireland on Wednesday.
The PPS said he appeared “before a court in Dublin where he was remanded in custody until 22nd February”.
PPS Assistant Director Marianne O’Kane, said: “Senior prosecutors, from both the PPS’s Serious Crime Unit and Appeals and International Section, have worked closely with the PSNI investigating team over recent months to expedite the prosecution decision in this case and commence extradition proceedings.”