What was Esther's (of the Book of Esther) covenant with God?

was it that she had deep faith and trust in him to help her through all of difficult times?

Why is her covenant with God so important?

was it because she needed/ relied on her faith and God to guide her/ give her courage when she was saving the Persian Jews?

Are these answers OK? Is there anything I'm missing? any sites I should look at?
thanks