Frada chose to tell Millard. Arthur's bluff only made her more worried. She was afraid that Arthur was increasingly controlled by his sister. Arthur might do another risky thing for Holly.
It didn't matter if Frada had to die or was tortured for Arthur. She was willing to be tortured by Arthur any time, but she couldn't let Holly have him.
"Poison can't kill him, you have to kill Felix straight away." That morning as the sun rose, Frada gathered all of Millard's spies to carry out this important task.
As she expected, Millard happily ordered her to finish Felix. They didn't have to wait for this curse to end. If Felix died right now, Millard would take his place and hold a war between humans and werewolves.
Frada knew Millard was actually not interested in becoming King, if Felix had followed his scenario to lead the war, he wouldn't have to step on the throne.
Everything has been decided. The King would lose his life because he refused war.