A "loud sigh" means she thinks you are an idiot at that moment, and wonders why she is wasting her time standing here arguing with you over "Nothing".

一声“大声叹息”意味着她认为那一刻的你是一个白痴，而且不明白自己为什么浪费了这么多时间站在这里来跟你争论“无关紧要的事”。

youdao

We all breathed a sigh of relief when it was over.

事情过去后，我们大家都松了一口气。

《牛津词典》

There are no birthday CARDS to sigh over - these days who would know?

没有生日卡，叹息—现在还有谁知道他的生日？

youdao

Sites like Twitter and (sigh) Google Plus allow connection between strangers, as do countless topical forums and communities all over the web.

FORBES: Absolving Silicon Valley of Its Social Media Sins