I’d suggest that women are definitely needed within the setting simply as part of the peasantry, as they make-up a larger percentage of most human populations.
Following on from that trail of thought, on female warriors, if female assets (body types) are introduced it seems like a missed opportunity not to allocate a slither (1/10th-20th ?) of the recruitment pool to the ladies, that you needn’t even recruit.
More interestingly adding ladies as potential soldiers of fortune could facilitate story events like fights over sexist remarks and assault, alongside contributing some grim backstories.
In terms of having to fight ladies, I would not expect to see any women in professional armies, however perhaps a wildling force would not be opposed to female archers, bandits might take whoever will join them, and upon being attacked a civilian caravan will muster whoever they can.
Point blank it would make a lot of sense to have female representation and availability as a recruitment option, it just boils down to keeping the level of representation proportional to the setting. i.e. brienne of tarth being an oddity rather than the norm.