She has had enough of his constant complaining.

has 是动词 have 的第三人称单数现在时形式，表示"拥有"或"经历"。 had 是动词 have 的过去分词形式，在这里与 has 构成现在完成时，表示"已经经历"。 enough 是形容词，意思是"足够的"，在这里表示"达到忍受的极限"。 has had enough 是一个固定搭配，表示"已经受够了"，强调对某种持续负面状态的忍耐达到极限。