Unlike other Shapers in the Council, Astoria wishes to be on good terms with the rebels which is best illustrated by the fact that she allows rebels on her lands.
Also, unlike the other Council Members, she believes that the Members should be active in their part as a leader. She believes that the leaders themselves should help when something wrong happens instead of sitting in a chair and ordering people. This is the reason why she helps the protagonist (if you are a Shaper) when the protagonist tries to destroy Ghaldring.
Alwan seems to view her with great distaste. He strongly disagrees with her views and, unlike her, wishes that she would destroy the rebels.
Rawal wishes that all of the other Council members owe something to him so that he would remain in good reputation. This is why he asks the protagonist to look for the Shadow Road.
Helping Out the Pro-Shaper Protagonist
If the protagonist chooses to be a pro-shaper and is given the mission to destroy Ghaldring, Astoria will help by giving the protagonist a stone which, when thrown at the doors to the west, would make the doors collapse and make sure that Ghaldring wouldn't run away.
In Alwan Ending
If the protagonist sided with Alwan, Astoria would never be able to rise to Head Council Member and would have people occasionally trying to assassinate her. In the end, though, she would be happy and never waver in her beliefs.