She kept stumbling through her words during the interview because of nervousness.

stumbling 是动词 stumble 的现在分词形式。stumble 本意是"绊倒、跌跌撞撞地走"，引申为"结结巴巴地说"或"说话不流畅"。这里形容因为紧张导致说话不连贯、磕磕绊绊的状态。