Praise be to Allah.
This house is to be divided as follows:
The house is to be divided among all the heirs, namely the mother and the seven sisters, just as if they were all still alive.
Each of the daughters who are still alive should take their share of the house. As for the sisters who have died, their shares are to be taken by their heirs as prescribed in sharee‘ah, such as their children and others.
After that, there remains the deceased mother’s share of the house. This is to be divided among her heirs as prescribed in sharee‘ah, namely all her daughters, both living and dead, if she died before her daughters. However, if some of the daughters died before the mother, the mother’s estate is to be divided among those who were still alive (at the time of the mother’s death).
However we advise you to refer this matter to the nearest Islamic court, so that the court may examine the matter and divide the estate among you according to shareeah.
And Allah knows best.