What did Queen Athaliah scream when she saw young Joash crowned at the temple?

Answer: "Treason! Treason!"

Seeing the boy king by the pillar and the people rejoicing with trumpets, Athaliah tore her clothes and screamed, "Treason! Treason!"

“And she looked out and saw the king standing by the pillar, according to the custom. The officers and trumpeters were beside the king, and all the people of the land were rejoicing and blowing trumpets. Then Athaliah tore her clothes and screamed, “Treason! Treason!””— 2 Kings 11:14 (BSB)