The Mishna Berura (classic work of Halacha by Rabbi Yisrael Meir Kagan, the "Chafetz Chayim," Lithuania, 1835-1933), in discussing the Hallel recitation at the Seder (Siman 479), makes the point that the women at the Seder should not recite the Hallel aloud, because of the Halacha forbidding women to sing in the presence of men ("Kol Be'isha Erva").
Rabbi Yosef Shalom Elyashiv (prominent Halachic authority in Jerusalem) notes that this issue arises even earlier in the Seder, with regard to the Ma Nishtana, the child's asking of the four questions, with which we begin the Maggid section of the Seder. Rabbi Elyashiv says that already from the age of three a girl should not sing in the presence of men. Therefore, it would be improper for a young girl to sing the Ma Nishtana at the Seder, unless no males other than her father and brothers are in attendance. If other men, including relatives from the extended family, are present at the Seder, a girl aged three or above should not sing the Ma Nishtana.
