Is the money shared between a deceased mother and her daughter considered an inheritance, and must the daughter inform her siblings about it? And what about the house that the mother intended to give to her adult grandson?

The heirs of the mother are entitled to all the wealth she left behind, and they divide it according to the prescribed shares and legal portions, with none of them having a right over another, in accordance with the Almighty's saying: "For men is a share of what the parents and close relatives leave, and for women is a share of what the parents and close relatives leave, be it little or much - a share ordained." [An-Nisa: 7].