"When Esther's words were reported to Mordecai, he sent back this answer: 'Do not think that because you are in the king's house you alone of all the Jews will escape.'" NIV translation
Mordecai reminded Esther that she was Jew and the edict applied to all of the Jews. It could not be changed and so there was no chance of her being the lone survivor.
"'For if you remain silent at this time, relief and deliverance for the Jews will arise from another place, but you and your father's family will perish. And who knows but that you have come to royal position for such a time as this?'" NIV translation
Mordecai continues to explain to Esther that silence is not an option as she will perish. He demonstrates his faith by trusting that, whether or not she agrees to go to the king, God will deliver His people. He asks her to think about the reason that she is in her royal position.
In Ephesians 2:10, we are told that God has prepared things for us to do (just as He had for Esther). Like her, we can choose to obey and follow the course He has set for our lives or we can ignore His Spirit. If we choose to obey, we will be blessed but, if we choose to ignore, God will use someone else to do His will.
"Then Esther sent this reply to Mordecai: 'Go, gather together all the Jews who are in Susa, and fast for me. Do not eat or drink for three days, night or day. I and my maids will fast as you do. When this is done, I will go to the king, even though it is against the law. And if I perish, I perish.' So Mordecai went away and carried out all of Esther's instructions." NIV translation
Esther's reply has a wonderful lesson for us today. When faced with this trial and decision, she called for fasting. As we see, this is denial of food and drink to oneself in order to focus on the things of God. It is significant that she asked for three days of fasting in that the number three is associated with the revealing of God's will throughout the Bible.