You are being insulting her!
你是在故意侮辱她!
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 这一句不能译作:"你现在在侮辱她!", 如要表达此意,
应该说: You are insulting her!
 为什么are being insulting会表示"故意侮辱"的涵义呢?
在回答这个问题之前, 让我们先对比一下下列两句的不同涵义:
  1. She is kind.
  2. She is being kind.

 从表层的结构持, She is kind的语义是"她是和蔼的",
从深层的结构看, is kind 是说明主语的特性的品质,
其内在涵义是: "她平日待人一向和蔼可亲". 
She is being kind的表层语义是: "她现在是和蔼的",
从深层结构看, being表示"目前"或"现在"的短暂涵义,
 它说明主体有意识进行的一个动作, 故其内在涵义为: "她平日待人并不和蔼,
 现在却故意装出一副和蔼可亲的模样".  在这种句型里,
being的意义相当于"故意地"(purposely or intentionally)

 下面再举几个类例:

They are being friendly.
他们摆出一副友好的姿态.
Tom is being polite.
汤姆装出一副彬彬有礼的模样.
Mary is being angry with me.
玛丽对我装作发脾气的样子.
Dick is being difficult.
狄克故意在找别人的麻烦.
They are being difficult.
他们在故意作梗.
HE is being naughty, isn't he?
他是在故意捣蛋,是吗?
"Mary, you're so pretty today"
"You're just being polite."
"玛丽,你今天真美."
"你真会说话."

最后一句的"You're just being polite."是回答别人称赞的用语,
相当于It's nice of you to say so, 故将其译作:"你真会说话."

 我們通過She is kind. 和She is being kind.的對比, 可以由此及彼, 舉一反三地想到:
 She is good (helpful, a fool, an angel, a nuisance...)
 不等于
 She is being good (helpful, a fool, an angel, a nuisance...)
 因為She is being good = She is behaving well.
 最后還需在此補充一句: 表示狀態的時候, "be"不能用于進行體. 例如, 我們不可以說:
 The Japanese sumo star Akebono is being fat.(只能說...is fat)