"un every way that matters" is more or less a synonime of "essentially", "in essence", "in a fundamental or basic way".

You could read this as "for the most part". Maybe one says "I am a woman in all the ways that matter". This could mean a lot of things, in this instance probably depending on the author. But let's imagine that the author believes that to be a woman means that you are attractive, with long hair, and big lips, and a fabulous cook. Then if the author is all of these, then "in all the ways that matter (to her or another)" she is a woman.