Breishit 18:15 says (Mechon Mamre / JPS in English):
Then Sarah denied, saying: 'I laughed not'; for she was afraid. And He said: 'Nay; but thou didst laugh.
Apparently, Sarah laughed because she didn't believe that G-d would create a miracle to let her give birth at such an old age. Some questions:
Apparently, G-d asks Avraham, why did Sarah laugh. The question is addressed to Avraham, but he doesn't answer. Why not?
If the question was asked to Avraham, how does Sarah know the conversation. Was she eavesdropping?
If Sarah did hear the question, and she understands that G-d is "angry" with her laughing, why does she deny and, essentially lie to G-d that she didn't laugh?
It says, "because she was afraid" ... afraid of what?
To me, the conversation seems somewhat "childish" - Like a parent asking a child, "Why did you do this", and the kid says, "No I didn't", and the parent answers, "yes, you did!" What is the Torah trying to tell us by including this whole back-and-forth conversation? Is it so important that we know that Sarah had a lapse of faith and then, denied that she did? What message is the Torah trying to teach us?