Learn English – “She had a smile on her face (,) (whilst) reading the texts” sentence meaning

1 "I haven't had a talk with her in a very long time.

2 I haven't had a talk with her a very long time.

3 I haven't had a talk with her for a very long time.

"Are all the above sentences grammatically correct? What's the difference in their meaning?"

In the above examples, numbers 1 and 3 are grammatically correct and have no difference in meaning. Number 2 is incorrect because it is missing a preposition to link "a very long time" with "I haven't had a talk with her."

"Why did she leave her car there?"

This is a loaded question. It says something is true, and then asks a question about it. It doesn't just ask why, it' also says that "She left her car there."

"Why would she leave her car there?"

This question is hypothetical. It asks us to imagine a situation that may or may not be true. This question still makes sense even if she doesn't have a car.

We can still use the "would" question even everyone agrees that she left her car theree. In which case as other answers have said, this means the question is allowing free speculation rather than asking for a certain answer and this is a subtle distinction that many people would not make.

If her leaving her car there is not accepted by everyone involved in the conversation then the distinction between a loaded question and a hypothetical question is very significant.