All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
The answer to your question involves two cases:
1- If the deceased woman was liable for obligatory Hajj in the sense that she was able physically and financially, and nothing prevented her from performing this great act of worship, then money must be taken from her estate to cover the expenses of performing Hajj on her behalf. However, if you feared that her heirs would never perform Hajj on her behalf and that they would take the money for themselves, then you are allowed to deputize someone to perform Hajj on her behalf without informing the heirs about the money utilized to cover the expenses.
2- If she died and wasn`t liable for performing obligatory Hajj in the sense that she wasn`t able physically and financially and in terms of obtaining the necessary visa, then the money she left is the right of her heirs and must be divided amongst them according to the rules of inheritance in Islam. And Allah the Almighty Knows Best.