Rian acted under two principles: logic and greed. All her actions were in accordance with this.
During the Tyranny of Dragons, under orders from her masters, Rian approached the Council of Lords of Waterdeep and offered help against the rising menace of Tiamat and the Cult of the Dragon, for which she gained a seat at the Council. She officially acted as one of the advisers of Lord Dagult Neverember and most of the councilors chose to ignore her real loyalties. Rian approved of all plans to stop the Cult, even the most cruel, and was in favor of an alliance with Thay.
If the adventurers gained the respect of the Zhents, then they offered their services at normal cost. However, unlike all the other factions involved, if Rian and the Zhentarim did not respect the adventurers, they still helped them for a substantial price.