How does one respond to a woman who claims that hastening to implement the full, detailed shar‘i hijab is an exaggeration and extremism, citing the Prophet's hadiths that encourage ease and gradualism in religion?

What a woman calls "gradualism" in obeying Allah's command is actually negligence and laziness, not the gradualism that scholars speak of. After the completion of the religion, the rulings of Islam are to be taken as a whole, and it is not permissible to gradually submit to them as was the case in the early days of Islam. Legal commands are tied to the مكلف's (accountable person's) ability, for Allah does not burden a soul beyond its capacity, as He (the Exalted) said: {So fear Allah as much as you are able}, and as the Prophet (peace and blessings be upon him) said: "When I command you to do something, do of it as much as you are able." This does not mean gradualism in legislation, but rather obligation according to one's ability.