A/N: Yeah, I apparently became obsessed with this film without noticing. Go figure. The former starts right after Thor's banishment; the latter after Loki goes. Movie spoilers.
Odin put a hand on Frigga's shoulder and she smiled up at him. Not a happy smile, but one that showed her certain that he had done the right thing. That there was no doubt in her mind, and he had no need to worry.
Loki had learned to lie from somewhere, after all.
Frigga kept the face up, when Sif doubted, or Loki looked particularly like he was hiding something. Frigga knew Loki probably felt guilty, since he had brought Odin down on them. Even without that, Loki was bright enough to see a hundred ways he could have stopped Thor, in retrospect. Frigga knew the feeling, that if she had just told someone the right thing here…but she also knew Thor. Once he got started, Loki could not have stopped him. None of this was Loki's fault.
Frigga appeared the perfect caregiver. She walked through the castle, gave comfort where it was needed, and did not let her face slip.
Then her husband fell into the Odinsleep.
She blinked when she heard the news, honest surprise and honest worry plain on her face before she could consider masking either.
She went to Odin and stood by him. When the frost giants attacked, she was too worn to think. She picked up the sword with no strategy, moved on instinct, and struck one down.
Loki had learned more about lying than anyone ever meant to teach.
Frigga knew sometimes people hid their emotions, and had seen that Loki was hiding something, but she never realized…never thought…
Frigga had seen the flashes of jealousy, and knew enough to give Loki some favor over the days before the coronation. Thor would be king, but both sons would always have their own places in Frigga's heart. Loki needed to know that.
Perhaps that was how she missed it. Frigga was too wrapped in comforting her Loki, then worrying over her Thor and her Odin. Already too much to take in at once, never mind if she had taken the time to contemplate that one of her sons, her Loki, could betray anyone like this. She knew when he was hiding something, and had always figured out what, but this time he had too many reasons. Brother becoming king when he wanted to be, then brother banished—maybe Loki even blamed himself, since he had called Odin. And then his father in the Odinsleep… Too many reasons. Too many choices. Wrong once, just once, and this is where it left her. With Thor, Sif, Fandral, Hogun, and Volstagg nearly dead.
Frigga took her comfort where she could, without giving too much away, because she had been too incautious, and now had to watch everyone. She hugged Thor, or squeezed his shoulder, or kissed him goodnight. A welcome home, but also a reminder for her, that one of her sons was home. That Thor had never been as good at hiding his emotions as Loki, and there was less need to worry, though she did. She worried what else she might be missing, in the son she had left, or in Sif, or in Fandral, or—not in Odin…
Too much, again. But if this was what happened when she let it be too much once, then she could never use that excuse, could she?