A noble lady was required to take on her husband’s responsibilities when: Her husband was away
At that time, there is a clear social expectation on women's position within every marriage. The men are expected to be the leader while the women were expected to be completely submissive to the men.
When the husband was away, the social standing that the noble women have stay with them regardless of the husbands' absence. This is why they can take over husband's responsibilities.