Praise be to Allah.
The woman in ihram is not allowed to wear the niqaab or burqa‘ (coverings for the face), because of the report narrated by al-Bukhaari (1741) from Ibn ‘Umar (may Allah be pleased with him) who said: The Prophet (blessings and peace of Allah be upon him) said: “The woman in ihram should not wear a niqaab or gloves.”
Ibn Qudaamah (may Allah have mercy on him) said: Ibn al-Mundhir said: The view that the burqa‘ [and niqab] is makrooh [for the woman in ihram] is proven from Sa‘d, Ibn ‘Umar, Ibn ‘Abbaas and ‘Aa’ishah, and we do not know of anyone who differed concerning that... But if the woman needs to cover her face because men are passing near her, then she should let down the cloth from the top of her head over her face. That was narrated from ‘Uthmaan and ‘Aa’ishah, and is the view of ‘Ataa’, Maalik, ath-Thawri, ash-Shaafa‘i, Ishaaq and Muhammad ibn al-Hasan. We do not know of any difference of opinion concerning that. That is because of the report narrated by ‘Aa’ishah who said: The riders used to pass by us when we were in ihram with the Messenger of Allah (blessings and peace of Allah be upon him). When they drew level with us, one of us would let down her jilbaab from her head over her face, and when they had passed us, we would uncover our faces. Narrated by Abu Daawood.
Al-Mughni (3/154). The hadith of ‘Aa’ishah was classed as saheeh by al-Albaani in his book Hijaab al-Mar’ah al-Muslimah.
Based on that, the woman in ihram may cover her face with something that she lets down from the top of her head, and not with a niqaab or burqa‘. The Afghaan niqaab, according to what we have heard, is like the burqa‘, so it is not permissible for the woman in ihram to wear it.
And Allah knows best.