Ragnhildr the White is the jarl of Ribe and thus the leader of the Ribe faction. She also rules Denmark as a direct vassal of Sigurdr Hringr, the king of the realms. As a result, she is most powerful jarl you will meet during the game. She and your father knew each other well and as a shieldmaiden, she has fought in some major battles as well. She is a neutral party in your struggle against Skule.
Prologue and first act
You will see her the first time at the start of the game during The Feast quest. When you talk to her during the feast and say that you will serve the king, you can earn one reputation point for her faction
You will meet her again shortly after the funeral in first act.
During the Althing, you will meet her the last time. In case you still need aid against Skule, she will say that she can not offer her aid due to being the ruler of Denmark as a direct vassal of Sigurdr.