Q. A woman that because of her need to care for her children attends Megilah reading late at 9.00 PM, can she eat before?
　
A. Shulchan Oruch (O.C. 652,2) prohibits eating before one complies with a mitzvah. Mishnah Berurah (ibid, 7) permits in need drinking small amounts or eating a snack that is not bread or mezonos.

It is advisable in such a case for one to ask someone else to remind him/her to attend the Megilah reading. (Mishna Berurah (692,16 – Nitey Gavriel Purim 11,6).

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a