Vidar's mention of having seen Sigyn had Frigg's gaze looking immediately to her husband. Odin would know what Sigyn had once meant to her. She was very, very dear to the Norse Queen. A dear friend lost in tragedy and to time. Frigg had spoken very little to Sigyn in the time that followed Baldr's and eventually.. Hod's deaths. Mostly out of heartache, for it pained her great deal to lose her sons to her friend's devious ways. And Frigg did place the majority of the blame on Loki.
Then... well, to say all hell broke loose wouldnt' be an understatement. She knew what was about to happen. Not the gritty details, not specifically what had happened, just that Sigyn and the boys were in danger.
She never forgave herself for locking herself up in Fensalir and weeping while her husband roamed the Nine Worlds -neither of them able to stop the events that unfolded form unfolding. She wanted to see her former friend. Not to make amends. That was fool's errand. She and Sigyn would never be friends again, she feared. And the Foremost Among the Asyniur wouldn't be able to right the wrong done to Narvi and Vali either. All she could do is offer her condolence and assurance that they would be left to be.
Nodding in agreement to her husband's statements, Frigg sighed and squeezed his hand. This was a very difficult conversation for her as she had very strong feelings against Loki from day one of her having met him. But, there wasn't much to be done about it now. “Avoidance is best,” she said, knowing full well that eventually she may try to seek Sigyn out and hope she doesn't get punched. “We don't want to provoke or slight. We have all seen what he is capable of when he feels slighted.” Which was a clear reminder not only of his hand in Baldr's death, but in his rather blatant murder of Fimafeng in cold blood. Aegir's servant, who did nothing, was slain by Loki in cold-blood in a drunk rage.