When distributing the share of our mother that she left after her death, should what was distributed before her death be collected and distributed among the aforementioned children, or should her share be distributed only according to Islamic law?

If the sale that took place during the mother's lifetime was a valid sale, and she was of sound mind and discretion, and she gifted a portion of its price to her children, then this is a completed gift. After her death, only the amount she kept for herself should be divided. However, if the sale was invalid because she suffered from Alzheimer's or was not of sound mind, then the sale is invalid, and the subsequent division of the price among the children is also invalid.