She kept money from the sale of her mother’s land and allocated it for maintenance of the family home. Does she have to tell the other heirs?

Praise be to Allah.

If this money came from the sale of your grandmother’s land, and your mother and aunt kept it and said that it is for the maintenance of the house, then what you must do is inform the other heirs of that, because as soon as your grandmother died, the wealth became theirs. Then it is up to them: if they wish, they may allocate it for maintenance of the house, or if they wish, they can share out the wealth, even if that leads to locking the house. By informing them, your mother’s duty will be discharged, and there will no longer be any blame on her  for keeping the money without informing the heirs about it.

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: The transfer of ownership of wealth through inheritance is compulsory. Allah, may He be exalted, says (interpretation of the meaning):

{And for you is half of what your wives leave} [an-Nisa’ 4:12]

{And for one's parents, to each one of them is a sixth} [an-Nisa’ 4:11].

Therefore, if one of the heirs says: I am well off and I do not want my inheritance from So-and-so, we say to him: Your share of inheritance is established and it is yours whether you like it or not, and you cannot refuse it. But if you want to give it up to one of the other heirs or to anyone else, then that is up to you, after it has come into your possession." (Ash-Sharh al-Mumti‘  2/142).

It is not permissible to use this money for maintenance or anything else, and it is not permissible for your mother, if she is still alive, to do that except with regard to her share of that wealth. As for the share of the other heirs, it belongs to them and disposing of it without permission is a transgression [against their rights] and is haraam. The same applies to concealing it from them and depriving them of making use of it. Allah, may He be exalted, says (interpretation of the meaning):

{O you who have believed, do not consume one another's wealth unjustly but only [in lawful] business by mutual consent} [an-Nisa’ 4:29].

The Prophet (blessings and peace of Allah be upon him) said: “Your blood, your wealth and your honour are sacred to you, as sacred as this day of yours, in this month of yours, in this land of yours. Let those who are present convey it to those who are absent.” Narrated by al-Bukhaari (67) and Muslim (1679).

And he (blessings and peace of Allah be upon him) said: “It is not permissible to take a person’s wealth except with his willing consent.” Narrated by Ahmad (20172); classed as saheeh by al-Albaani in Irwa’ al-Ghaleel (1459).

So hasten to inform the other heirs, and give them the choice between maintaining the house or sharing out the wealth, and ask them to forgive your mother, if she hid this wealth from them.

And Allah knows best.