All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, you should know that the oldest age that is reported about 'Aa'ishah when the Prophet, sallallaahu ‘alayhi wa sallam, consummated the marriage with her, is ten years old, as reported by Ibn 'Abdul-Barr in his book At-Tamheed. However, he stated that the most authentic narration in regard to the chain of narrators, is the one narrated by Hishaam ibn 'Urwah who reported it from his father, from 'Aa'ishah that the Prophet, sallallaahu ‘alayhi wa sallam, consummated the marriage with her when she was nine years old. [Al-Bukhari and Muslim]
Therefore, we do not think that there is a problem with regard to the narration which you mentioned in the question about the statement of 'Aa'ishah ''I was a young girl playing when the verse of Allaah (which means): {Nay, but the Hour is their appointed time (for their full recompense), and the Hour will be more grievous and more bitter.} [Quran, 54:46], was revealed."
Chapter Al-Qamar [Quran, 54], was revealed seven years before the battle of Badr, as Ibn 'Abbaas stated, and this is mentioned in the interpretation of the Quran by Al-Qurtubi . The battle of Badr took place in the year 2 A.H. The Prophet, sallallaahu ‘alayhi wa sallam, married her in 1 A.H., in the month of Shawwaal. Therefore, there are six years between this marriage and the revelation of the chapter. Hence, her age was three years or four years according to the different narrations which state that she consummated her marriage at the age of nine or ten. At this age – the age of three or four years – a young girl is conscious. Thus, it is not strange that 'Aa'ishah remembered the revelation of the above verse at this young age. In fact, today we see some young children at her age, who are less conscious and less intelligent, who memorize many chapters of the Quran. Indeed, the scholars of Prophetic narrations consider what a young child hears and memorizes as acceptable and relied upon.
Undeniably, Imaam Al-Bukhari titled a chapter ''At what age may a youth be listened to (i.e. a quotation of a narration be acceptable from a boy).” In this chapter, he mentioned a narration by Mahmood ibn Ar-Rabee' who said, ''When I was a boy of five, I remember the Prophet, sallallaahu ‘alayhi wa sallam, took a sip of water from a bucket (used for getting water out of a well) and splashed it on my face.'' Furthermore, we have already clarified that it is possible for a girl to be like a woman at the age of nine years (i.e. reach puberty), especially in warm countries like the Arabian Peninsula. For more benefit, please refer to Fatwas when she married">82962 and 82960.
Finally, it should be noted that a seeker of knowledge should ask a question seeking knowledge and not objecting, because a person benefits more when seeking knowledge and abiding by the good etiquettes and manners when asking a question, especially in a matter like this one, about which a narration is proved to be authentic by the two most reliable and trusted books, which are the books of Prophetic narrations reported by Imaams Al-Bukhari and Muslim .
Allaah Knows best.