is this sentence understandable?
First lady had been called “mother of the nation” at ancient times. She is a symbol of a country as the head of the state.

Question

Answer

It is understandable, but the first sentence is slightly incorrect. 
Considering she is no longer called "mother of the nation" it would look more like:

First Lady was called "Mother of the Nation" in ancient times. She is a symbol of the country as the head of the state.