Is it permissible to specify a certain number of Istighfar for a deceased woman, as a daily litany, in order to do it in abundance?

Seeking forgiveness (Istighfar) is one of the remembrances (dhikr) that a Muslim is encouraged to recite frequently for themselves, for their parents, and for the believers. There is no objection to specifically seeking forgiveness for a particular woman. It has been reported that the Prophet, peace and blessings be upon him, used to seek forgiveness a hundred times a day and night. So, whoever wishes to adhere to this number in imitation of him, it is good. And whoever wishes to increase it, there is no harm, as long as they do not believe there is a special virtue in that increase. It is preferable not to continuously adhere to an amount that has not been mentioned in the Sunnah.