Literally: “The woman… height is big.”

는 is the topic marker. I'm this case, the topic is the woman.

가 is the subject marker. The subject here is height.

This sentence is stating something about the height in relation to the woman. So while 는/은 and 가/이 are used interchangeably in some cases, this is one where they are used with their finer nuances.

What does 키가 and 큽 means?

I am Korean and exactly 'the woman is tall' is right

The sentence structure is similar to Japanese:
女子は 背が 高い。

어렸을 때 저는 키가 크워요