ואת שבע הנערות הראיות לתת לה
“And seven maids who were fitting to be given to her.” (Esther 2:9)
When Esther was taken to Achashveirosh’s palace along with the other candidates to replace Vashti, she found favor in the eyes of Hegai, who was in charge of guarding the women, and he arranged for her to have seven young women who were fit for her. In what way were these seven young women specifically suitable for Esther? In his commentary on the Megillah called Megillas S'tarim, the Nesivos HaMishpot (Rav Yaakov Lorberbaum of Lisa) explains that even though Esther refused to disclose her identity or nationality, she was miraculously provided with seven girls to assist her who were all Jewish. This made her feel more comfortable, and it was a sign from Hashem that He had not forgotten about her even while she seemed to be abandoned and forlorn in the king’s palace.
What specifically did these young women do to take care of Esther? The Targum writes that they made sure to bring her kosher food. Additionally, the Medrash teaches that the reason Mordechai sat in front of the palace gates every day was to try to ensure that Esther would not eat any non-kosher food. Why were Esther's servants and Mordechai more concerned about her eating kosher food than about her observing other mitzvos?
The Vilna Gaon writes that the Jewish people in that generation committed two sins for which they were threatened with destruction. One was that they went to Achashveirosh's party and ate non-kosher food there, and the other was that they bowed down to a statue in the times of Nevuchadnetzar. To rectify these two sins, they had to engage in both teshuvah [repentance] and fasting. The teshuvah was intended to rectify the sin of bowing to the idol, and refraining from eating during the fast corrected the sin of eating the food at Achashveirosh's party. For this reason, there were two redeemers in the Megillah: Mordechai and Esther. Mordechai rectified the sin of bowing down to the statue through his refusal to bow down to Haman, while Esther corrected the sin of eating at Achashveirosh’s party.
In light of this explanation, Rav Yitzchok Sorotzkin writes that we now appreciate why there was such a specific focus on Esther not eating non-kosher food while she was in the king's palace, as her role was specifically to rectify this sin, which she did through her dedication to ensuring that she only ate kosher food. He adds that perhaps this was one of Mordechai's deeper intentions in commanding Esther not to reveal her identity, because if Achashveirosh would know that she was an observant Jew, he would gladly give her kosher food, and she would lose the challenge of fighting for it and the merit that she created through her struggles and sacrifice.