We meet Esther in chapter 2, verse 9 as a maiden. In the Hebrew, the word is “na’ara” which is a young woman of marrying age, but the word is also used to describe a girl from toddler to adolescent age. So as customary in the middle east, her description fits a young girl up to her adolescent years, and who is eligible for marriage. She would be as the Virgin Mary, perhaps 11 or 12 years old.
In chapter 2, we read of beautifying ointments and salves to protect her young skin, and her purification. She lived with other young women, preparing for their presentation before the King.
At the removal of Vashti as Queen . . .