Why do women have to say Birchas Hatorah they are not commanded to learn Torah as men are?
The Igur brought by the Beis Yosef(אר''ח סימן מ''ז) answers since they are responsible to know the Halachos of the Mitzvos they are responsible for they must therefore make a Bracha. The Minchas Chinuch(מצוה ת''ל ס''ק ה) asks on this that they are responsible to know the Halacha,but its not because they have to learn its because they have to know what to do, so why make a bracha? The Igur answers non the less since they are responsible for Teffilah and saying Korbonos they make the Bracha.The GRA(באר''ח סימן מ''ז) answers like all Mitzvos that are time bound, if they want the can make the Bracha the same applies to Birchas Hatorah.
(The Mishnah Berurah(אור''ח סימן מ''ז) based on this says therefore women can not be motzeh men since they are not responsible for the Bracha they choose to make so they can not help a man for his chiyuv is greater.)