Is it permissible for a woman who wears the niqab, and who is unable to cover her head completely due to her eyesight and a feeling of breathlessness, to wear a medical or cloth face mask that covers only the nose and mouth, along with covering her hair, in order to perform Umrah?

A female pilgrim in the state of ihram is prohibited from covering her face with a niqab or anything similar, such as medical masks, unless there is a necessity. In such a case, she must offer a fidyah (expiation), because masks cover a part of the face, and jurists have explicitly forbidden this. If the questioner is compelled to cover her face from men, then she should let something hang over her face from above her head, or she may wear the masks out of necessity and remove them afterwards, and the fidyah becomes obligatory upon her.