What level of obligation do women have in the commandments of Purim?
Generally speaking, women are not obligated in Mitzvot aseh she-hazman geramah – positive commandments that are dependent on time. Thus, women are not obligated to sit in a Sukkah on Sukkot, nor are they obligated to wear tzitzit or to lay tefillin, which are only done during the day. Based on this principle, we would anticipate that women would not be obligated in the mitzvot of Purim, either.
Rabbi Yehoshua ben Levi teaches that women are obligated to hear the reading of the Megilla, she’af hen hayu be-oto ha-nes – that they were partners in the miracle of Purim. There is a difference of opinion regarding this teaching. According to Rashi and most of the commentaries, Jewish women were included in Haman’s decrees of destruction, and are therefore obligated to participate in the thanksgiving festivities that celebrate the rescue of the Jewish people. Rav Hai Gaon, the Rashbam and others argues that the Gemara’s intent is that Jewish women played a crucial role in the miracle, in that Esther orchestrated the events that led to Haman’s discovery and hanging.
In either case it is clear that women are obligated in the mitzvot of the day. How this affects women and their own reading of the Megilla is the source of some dispute.
According to Rashi and the Rambam it appears that women are obligated in reading the Megilla and therefore can read for others, as well. The Meiri and the Ritva rule that women are obligated in the mitzva, but they nevertheless cannot read for others because of an external reason, for example because it is not appropriate for the honor of the community for women to play such a public role. Finally there are those who suggest that women cannot read for others because their obligation is not to read the Megilla, but only to hear the Megilla.