She is compartmentalizing the documents into different folders to work more efficiently.

compartmentalizing 是动词 compartmentalize 的现在分词形式。compartmentalize 由名词 compartment（隔间、分隔区）加上动词后缀 -ize 构成，意思是"把...分成不同的部分或类别"。compartmentalizing 在这里表示"将文件分类整理"的动作。