In her surprise at seeing her son, she had momentarily betrayed herself.

看到儿子时， 她很惊讶，一时之间，她出卖了自己。

Fearing to betray herself, she slipped away, murmuring something about needing more paper.

由于害怕背叛自己，她溜走了，嘴里嘀咕着需要更多的纸。

She had betrayed herself, however, by a look and a blush, for though an absent man, the Professor saw a good deal more than people fancied.

可是她的神色与脸上的红晕却暴露了自己，教授尽管是一个粗心大意的人，却见多识广，远远超出人们的想像。