Why can 〜ようと思う express someone else’s volition other than the first person?

Question

あんな状況の中、あんな文面で士道からお誘いがあったなら、普通の女子であれば警戒するに決まっている。わざわざ馬鹿正直に一人で待ち合わせ場所に来ようとは思わないだろう。すっぽかされなかっただけまだ幸運だったかもしれなかった。

Context: In the name of 士道, a letter was sent to 亜衣, one of 士道’s classmates, telling her (亜衣) to go alone to meet 士道 in a cafe. But it turned out that 亜衣 went there in company with her friends.

Hi. I know the bold part is a very basic Japanese sentence pattern 〜ようと思う. And I was taught that the pattern was only used to describe the intention of the speaker “me”, for example, 今日会社を休もうと思う (I don’t want to go to work today). But why can the pattern be used for someone else’s intention/volition as in this text? Please shed some light on it.

Thank you.

Answer 1

彼女は来ようと思う is wrong simply because ～と思う (followed by nothing) is already incorrect if it's said with a third-person subject.

• 思っている/言っている with third person subject?
• Why do we have to use ている form of 思う with third person subject

But the following sentences are perfectly fine:

• 彼女は来ようと思っている。
• 彼女は来ようと(は)思っていない。
• 彼女は来ようと思うだろう。
  (I believe) she will want to come.
• 彼女は来ようと(は)思わないだろう。
  (I believe) she won't want to come.

来よう is just a quote, and it can be replaced by almost anything. For example, 彼女は人間が150歳まで生きられるようになるとは思わないだろう is a valid sentence.