In Season 1 she is in a position of power, being the wife of the Earl of Kattegat. However, when Ragnar kills Haraldson, she is left having to eke out her position. She successfully does this by becoming a servant to Lagertha. Siggy and Rollo start a relationship but when a plague strikes Kattegat, Siggy then loses her daughter.
In season 2, Siggy continues in her power play, not only maintaining her relationship with Rollo, but also starts one with King Horik.
(Photo Credit: History Channel, Metro-Goldwyn-Mayer Studios Inc.)