It's not easy to know you've royally messed up. So, when the princes were transformed into twelve ravens, the Princess accepted her imposed seven years of silence gladly.
When the King put her on the pyre after believing his mum's lies, she still remained silent. But as the curse was broken and her brothers rescued her just in time, she said to the King who wanted her back:
'Get away from me, you wimp, run to mummy's skirts'.
Her twelve brothers surrounding her protectively, the King backed down.
Morality: Don't marry a girl with twelve burly brothers. It spells trouble.