她们开心极了用英文怎么说

"她们开心极了"用英语可以表达为"They are extremely happy"。

这句话的来源是英语中的表达方式，"happy"在这里表示"快乐的"的意思，"extremely"是一个副词，表示"极其"的意思。

例句：

They are extremely happy because they just got married. 他们非常开心，因为他们刚刚结婚。
I could see that they were extremely happy when they received the good news. 当他们收到好消息时，我看得出他们非常开心。
They were extremely happy when they won the lottery. 他们赢得了彩票，非常开心。

中文翻译：

他们非常开心，因为他们刚刚结婚。
当他们收到好消息时，我看得出他们非常开心。
他们赢得了彩票，非常开心。