She looked as though she was about to deliver some very bad news.

looked 是动词 look 的过去式，表示"看、看起来"。 as 在这里是连词，表示"如同、像"。 though 在这里是连词，表示"虽然、尽管"，但在这个固定搭配中不单独表达让步含义。 as though 是一个固定搭配，表示"好像、仿佛"，用来引导一个虚拟或假设的情况。