How do we know that women are exempt from positive time-bound commandments? It's learned from tefillin, which is linked to learning Torah. Or tefillin could be linked to mezuzah - but that would make women obligated in tefillin! Also, delving into the mitzvah of Re'iyah, which is specifically for males - implying that women are obligated in other positive time-bound commandments. But maybe that's just Hakhel? Note that there's no middle ground between a women under her father's auspices or her husband's. But the original examples do seem to provide the source in the most simple (albeit complicated) manner.