Etaya was supposed to come in two days. Iona had asked her to come because the time was coming. Iona knew that after the marriage Ileus and Anastasia would be taken to Silver Vales. The plan was to attack them and abduct the two when they were out of Draoidh. Etaya would take them away as part of her deal. As for Iona, she would use the moment of chaos and enter Eynsworth Palace where she would kill Adrianna and Dmitri and take charge of the throne and would call her Master.
The plan was simple, but needed coordination. The limitation was that only the necromancer's magic could take her inside the kingdom. And necromancer magic was banned. It had to be practiced secretly.