But she felt it creeping out of the sky。

参考译文是：他感到它从天空中升起。

out of A, 即从A的外面看某物从A从脱离出来

(1)out of 从…里面（拿、取）出来 (英文解释：If you take something out of the container or place where it has been, you remove it so that it is no longer there.)

I always took my key out of my bag and put it in my pocket.

我总是将钥匙从包里取出来放进口袋。

(2)out of 向（窗）外 （英文解释：If you look or shout out of a window, you look or shout away from the room where you are towards the outside.）

He went on staring out of the window.

他继续凝视着窗外。

He looked out the window at the car on the street below.

他望着窗下街头的那辆汽车。

(3)out of避开，未暴露于（太阳、雨或风） （英文解释：If you are out of the sun, the rain, or the wind, you are sheltered from it.） 

People can keep out of the sun to avoid skin cancer.

人们可以通过避免阳光照射来预防皮肤癌

(4)out of摆脱，脱离（尤指令人不快的事）（英文解释：If someone or something gets out of a situation, especially an unpleasant one, they are then no longer in it. If they keep out of it, they do not start being in it.）  

In the past army troops have relied heavily on air support to get them out of trouble.

过去，陆军部队在很大程度上依赖空中支援来摆脱困境。

The economy is starting to climb out of recession.

经济开始走出衰退。

The Salvation Army has worked in the big cities to keep endangered young people out of a life of crime.

救世军已经在大城市展开行动，努力使那些处于危险边缘的年轻人远离犯罪。

(5)out of在…之外；超过…界限 （英文解释If you are out of range of something, you are beyond the limits of that range）

Shaun was in the bedroom, out of earshot, watching television.

肖恩在卧室里看电视，听不见。

He turned to look back, but by then she was out of sight.

他转头看去，但那时她已经不见了。

(6)out of出于；由于 （英文解释You use out of to say what feeling or reason causes someone to do something. For example, if you do something out of pity, you do it because you pity someone）

He took up office out of a sense of duty.

他就任公职是出于一种责任感。

Some people have left out of embarrassment at what's happened to them.

一些人已经由于为发生在自己身上的事感到难堪而离开了。

(7)out of介词（通常指在对方不情愿的情况下）从（某人）身上（获得信息或工作成果）

'Where is she being held prisoner?' I asked. 'Did you get it out of him?'...

“她被囚禁在什么地方？”我问道，“你从他口里套出来没有？”

We knew we could get better work out of them.

我们知道他们可以做得更漂亮。

(8)out of由…（引起）；从…中（得到）

We all had a lot of fun out of him...

他给我们带来很多快乐。

To get the most out of your money, you have to invest.

要想把钱的收益最大化，就必须投资。

(9)out of缺乏；没有

I can't find the sugar — and we're out of milk.

我找不到糖——而且我们也没牛奶了。

(10)out of用…（制成）；由…（建成）

Would you advise people to make a building out of wood or stone?

你会建议人们用木材还是石头建房子呢？

(11)out of（表示比例）每…中

Two out of five thought the business would be sold privately on their retirement or death...

五个人之中有两个认为公司会在他们退休或去世时被私下卖掉。

In 99 cases out of a hundred this will be done more effectively by the army.

这件事让军队来做十之八九会更有效。

 网友引用句子时应该注意完整引用，不要自己随意断句。该句的完整结构及上下文如下：

There was something coming to her and she was waiting for it, fearfully. What was it? She did not know, it was too subtle and elusive to name. But she felt it, creeping out of the sky, reaching toward her through the sounds,the scents,the color that filled the air.

有种东西正向她靠近，而她正恐惧地等待着。那是什么?她不知道。那东西太微妙太难以捉摸了，她说不清楚。但是她能感觉得到它，它正悄无声息地从天空中逸出，穿过弥漫于空气中的声音、气味和颜色慢慢地向她靠近。

out of something: 从某东西中出来。

creeping现在分词短语作it的非限制性定语。有人称这种分词短语为补充语supplement。注意it和creeping之间的逗号，逗号明确表明分词不是宾语补足语。feel的这种用法不能接复合宾语结构，只能是单宾语，即名词或that从句作宾语。reaching现在分词短语为creeping的结果状语。

故事结局告诉我们，这段话中的it指的是freedom。