Except historically, women did have options in some places and times. Women in towns in northern Europe had an amazing degree of freedom in the high and late middle ages, which is what most fantasy is based on; in these situations (townswomen made up what, 10-15% of the overall female population?) they were actually legally more free than independent noblewomen; they'd be taught a trade from puberty, and if they married a husband in that trade they could help him, but if they didn't they could run a business independently (I ran across records of unmarried English tradeswomen who managed to support bastard children and send them off into respectable trades themselves) or, if they married a husband who did something different, were legally granted autonomy over their own businesses, to the point where their husband had no say over their wives' business transactions.
So. Granted, it wasn't done a ton of the time, but during a time-period fantasy chooses to focus on, a not insignificant population of women didn't have to make the choice between children and independence.
Yes, the same is true in the Japanese merchant class of the Edo period to some extent, and I find it a very interesting part of history, and highly relevant to microbusiness today (especially in Third World countries). On the other hand, it's not something a woman can choose in the time to which you refer - it's a class into which she is born.