Q. On a prior question (1985) you mentioned that it is not obligatory to answer amen on hearing the bracha of a woman. Is that true for all brachot women say?
A. Mishna Berura (124: 47) indeed mentions only a brocho recited by a woman on a mitzva shehazman gramma, (is time dependent), since they are not obliged to comply with those mitzvos, and not in the rest of brochos such as the ones recited on food.
Even on those time dependent brochos some Poskim maintain that one has to answer amen (Orach Yisroel p. 185, quoting Horav Y. Kamenetzky and Horav M. Feinstein zt’l).
Horav Shlomo Miller’s opinion is that it is a mitzva to answer.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a