have a cow 十分生气
have a cow中的cow并不指“母牛”，而是指“着急；慌张”等等。所以She must have a cow!表达的意思是“她一定气炸了，她一定十分生气”。
例如：
Wendy : When you told your mom you would be home around 2 am, she must have a cow!
温迪 ：你跟你妈妈说你会到凌晨两点才回家，她一定气死了。
May: You are right. My mum must be crazy.
阿美 ：没错，我妈妈一定都快疯了。