"For years, many salafi scholars have demonized women who reveal their faces" That doesn't sound like Salafis more like some extremist Kawarij types..Subhanallah! Yeah I'm aware many of these extremists do label themselves "Salafi" but yuck! How far are they from the path of the Salaf?? I pity your sister & any Muslima who has to deal with such ideologies. The truth is yes the niqaab is much debated even among the scholars of the salaf mainly due to the interpretation of the verse in Surah Ahzab where Allah says "Its better for them" Some scholars take that to be that its obligatory for all Muslimas as it was for the wives of the Prophet. But you have great scholars of the past like Sheikh Al Abani who debated that its "better for you" means its simply a highly recommended act & not obligatory.
However to spread the message that "that only niqab will bring them salvation. And women without face veil are naked " Sounds very extreme & thalaiban like! I hope the govt. cracks down on such campaigners as they could pose serious security concerns!