Ref. No. 1136/42-373
In the name of Allah the most Gracious the most Merciful
The answer to your question is as follows:
At the time of distribution, if all members were agreed, then the distribution is valid. Demanding redistribution later is not valid. However, in case the younger sister was not agreed at the time of distribution and justice was not taken into account in the distribution, then she can ask for redistribution.
And Allah knows best
Darul Uloom Waqf Deoband