In the present case - B as you know has a definite right in the property. Considering the facts that you've told me this is how it goes :-
D - C - B formed a coparcenory - each entitled to 1/3rd of total property. Now since C has expired. His 1/3rd would devolve in equal shares to A and B. Hence A has 1/6th of total property. B has a total of 1/2 of the total property.(her 1/3rd as a coparcenor + half of her father's 1/3rd).
Now as regards the cheque it is not very safe - cheque is always a conditional payment - and is as good as long as it is honoured......Once you are satisfied by your payment you can get a compromise decree passed in the aforesaid case on the terms that you desire.