Any change, great or small, would cause some unrest. Haste made waste, so the more drastic the change, the more intense the resulting unrest. Politics was personnel, after all. Political changes were ultimately changes in personnel, so the unrest they caused was naturally unrest among people.
A new ruler brought a new court. Now that Frigga was in charge, she would naturally dismiss those who did not share her aims, or who might even obstruct her policies, and replace them all with her own trusted people.
It would be best if those people left willingly, but driving them out was not difficult either. All she had to do was find a pretext and pin a crime on them. Was that hard?
Asgard had laws, but it had never been constitutional. Thus, those laws were royal law, and royal law was the King's law. Naturally, whatever the King said counted. This included declaring a law invalid or adding one whenever necessary—for example, reducing someone to the status of a little beggar.
The nobles and officials had some influence and room to resist, but before an absolutely powerful monarch, they could only bow their heads and submit.
Frigga was certainly powerful now. On one hand, the ministers had nominated her, and Odin had approved her appointment as regent, making her entirely legitimate. That was her legal foundation. On the other hand, the newly formed Valkyrie Corps provided military backing.
Frigga was no fool. She would not make a mess of things before she was ready. There had been some small moves early on, but the real sweeping reforms began after the battle at the Fel Scar Rift. Using her exquisite mastery of Magic and the vast amount of Fel Blood Sif had brought back, she expanded the Valkyrie Corps to ten thousand