Is it permissible to complete the six days of Shawwal fasting after its end, for one who fasted four days then menstruated at the end of the month?

Ramadan is fasted, then it is followed by six days of Shawwal, thereby earning the reward of fasting a lifetime. Scholars have differed concerning those who fast the six days not in Shawwal, whether due to an excuse or otherwise. Some are of the view that the virtue is attained whether they are fasted in Shawwal or after it. Others are of the view that the virtue is attained but with less reward than fasting them in Shawwal. And some are of the view that the virtue is not attained except by fasting them in Shawwal. Allah's bounty is vast, and reward and recompense are hoped for those who fast them in Dhul-Qa'dah as compensation for what they missed in Shawwal.