I believe the demons knew the Amazon queen would be trouble, likely by some divination or omniscience by Jul. When they had the opportunity to rid themselves of the queen, they took it. Loren was likely an accident since she only discovered the Hawk/Ember Blade by coincidence, in the Vork Lair or by being arrested by the Empire (as set up by Grob). Jul, again using omniscience, knew the queen left the Citadel with her servant. In the cut scene, Fost asks Jul if there were any complications. Jul said that Loren was looking for her mother and was very determined. So, I do not believe that kidnapping her mother was meant as a distraction. If anything, they probably wanted her to abandon her mother and take the role of queen, as Breza suggested, and because that is Citadel law.
It could be that the prophecy, or Jul's divination of the queen of the Amazons, was right but the wrong queen! Loren is pronounced as the next queen as soon as she returns to the Citadel with her mother.