变得慌张 meaning in English

lose one's nerves

The steady countenance which miss lucas had commanded in telling her story , gave way to a momentary confusion here on receiving so direct a reproach ; though , as it was no more than she expected , she soon regained her composure , and calmly replied ,
卢卡斯小姐乍听得这一声心直口快的责备，镇静的脸色不禁变得慌张起来，好在这也是她意料中事，因此她立刻就恢复了常态，从容不迫地说：