[General] I don't know what she's thinking about.

[Silverobama]

A woman I know wanted to learn English from me. She told me she wanted to learn and she even bought the book we were supposed to use. Later, she didn't reply my messages and didn't say the reason she doesn't want to learn. I thought she would learn but she didn't. I wrote a sentence to express the idea:

I really don't know what's she thinking about.

Is the italic sentence natural?

 

[GoesStation]

What's she thinking about is the interrogative form. Your sentence needs the declarative. Correct that error and your sentence will be okay.

 

[Charlie Bernstein]

A woman I know wanted to learn English from me. She told me she wanted to learn, and she even bought the book we were going to use. Later, she didn't reply to my messages and didn't say why she doesn't want to learn English anymore. I thought she would study English, but she didn't. I wrote a sentence to express the idea:

I really don't know what's she thinking[STRIKE] about[/STRIKE].

Is the italic sentence natural?

The expressions thinking, thinking about, thinking over, and thinking of have slightly different meanings.

Don't forget those commas!

(Cross-post.)

 

[jutfrank]

I don't think you mean to use thinking about. The idea is better expressed without about.

I really don't know what she's thinking.