Is it permissible for females to distribute their mother's money among themselves after her death, while withholding this money from the males, based on the mother's will not to inform them of its existence?

We ask Allah to forgive your grandmother for the transgressions she committed, which included: not being fair among her children in the gift (hiba), which is a religious obligation according to the hadith (definition) of Nu'man ibn Bashir: "Be mindful of Allah, and be fair among your children," and his (Prophet's) saying: "Do not make me a witness to injustice."

Also, her will to deprive her male children of inheritance is religiously forbidden.

Therefore, it is forbidden to execute her will, and what she gifted to her daughters is considered an inheritance to be inherited by all heirs, due to the injustice involved and because the daughters did not take possession of that gift before the grandmother's death.