Frigga's Odin's wife, and frankly speaking she doesn't have much to do here…save for one big scene. Most of the rest of the time, she's all 1950's First Lady: she smiles and waves and being seen instead of heard.
Turns out, though, she takes her role as mom very seriously. That applies to Loki as much as Thor, and when the L-Man feels the burn at being the redheaded stepchild, it isn't Odin who can reason with him: it's Frigga.
She finds the words to reach Loki after Odin falls into his enchanted slumber, and lets him know that it really isn't as bad as all that.
FRIGGA: He kept the truth from you so you would never feel different. You are our son, Loki, and we your family.