My mother has claimed an equal share in the whole property of 20acres in the year 2014. Is there any chance that she will get her equal share? and if so then what should be the documents or laws that we should use for the argument?
Since your maternal grandfather inherited the properties from his father, it became your grandfather's own and absolute property there by the character of ancestral property extinguished.
Now since your grandfather had already allotted 9 acres to his wife as gift or settlement, this portion belongs to your grandmother as her own property.
However your mother being one among the legal heirs of your grandparents she is entitled for an equal share in the intestate properties of your grandparents along with other legal heirs.
Since you have already filed the suit for partition and it is going on what else is the document that you want more to rely upon.
The case is legally maintainable and your mother is entitled for her legitimate share, the court will decide accordingly.