She placed her hand on her forehead theatrically and pretended to faint.

theatrically 是形容词 theatrical（戏剧的、夸张的）的副词形式，由 theater（剧院）加形容词后缀 -ical 构成形容词，再加副词后缀 -ly 构成副词。这里形容动作夸张做作，带有表演性质。