Pardon me? Muslims do not believe that? Was she a liar or are hadiths all false/weak? If these are not true then how can you believe anything is true in quran and hadiths.
Bukhari - Volume 5, Book 58, Number 234:
The Prophet engaged me when I was a girl of six (years). We went to Medina and stayed at the home of Bani-al-Harith bin Khazraj. Then I got ill and my hair fell down. Later on my hair grew (again) and my mother, Um Ruman, came to me while I was playing in a swing with some of my girl friends. She called me, and I went to her, not knowing what she wanted to do to me. She caught me by the hand and made me stand at the door of the house. I was breathless then, and when my breathing became Allright, she took some water and rubbed my face and head with it. Then she took me into the house. There in the house I saw some Ansari women who said, “Best wishes and Allah’s Blessing and a good luck.” Then she entrusted me to them and they prepared me (for the marriage). Unexpectedly Allah’s Apostle came to me in the forenoon and my mother handed me over to him, and at that time I was a girl of nine years of age.
Volume 5, Book 58, Number 236:
Narrated Hisham’s father:
Khadija died three years before the Prophet departed to Medina… He stayed there for two years or so and then he married ‘Aisha when she was a girl of six years of age, and **he consumed that marriage **when she was nine years old.
Volume 7, Book 62, Number 118:
Aisha said, “While the Ethiopians were playing with their small spears, Allah’s Apostle screened me behind him and I watched (that display) and kept on watching till I left on my own.” So you may estimate of what age a little girl may listen to amusement.
Volume 7, Book 62, Number 163:
The Prophet was screening me with his Rida’ (garment covering the upper part of the body) while I was looking at the Ethiopians who were playing in the courtyard of the mosque. (I continued watching) till I was satisfied. So you may deduce from this event how a little girl (who has not reached the age of puberty) who is eager to enjoy amusement should be treated in this respect…
Volume 8, Book 73, Number 151:
I used to play with the dolls in the presence of the Prophet, and my girl friends also used to play with me. When Allah’s Apostle used to enter (my dwelling place) they used to hide themselves, but the Prophet would call them to join and play with me. (The playing with the dolls and similar images is forbidden, but it was allowed for ‘Aisha at that time, as she was a little girl, not yet reached the age of puberty.) (Fateh-al-Bari page 143, Vol.13)