What does 2 Kings 11:14 mean?

She saw the king standing by the pillar, as was the custom, with the commanders and trumpeters beside him. Everyone was celebrating and blowing trumpets. Athaliah tore her clothes and screamed, 'Treason! Treason!' 2 Kings 11:14 - Modern Text Bible

(Athaliah realizes she's been overthrown and accuses the people of betrayal, but the crowd is united behind Joash.)