About the 'refusing to interact' thing. That barrier to interaction is actually being put up by the niqab wearer.
I was in a small university tutorial with a niqab-wearing woman some years ago. It was about eight people in the room sat in a circle, seven of whom could see and speak to each other normally, and one faceless person shrouded in black. Everyone was uncomfortable with this - EVERYONE, except, probably the niqab wearer herself. You could feel the awkwardness in the room, especially when the tutor tried to involve her in discussions (she never spoke voluntarily).
I was a good liberal who tried to pretend I was open minded and this was all fine, but pretty soon I realised it wasn't. It was not fine, it was weird, it affected the whole dynamic of the class that one person kept their face hidden behind a veil the whole time. And this was not about OUR prejudices. This was on her. She chose to put up that barrier (literally!) between us.
I know posters will say, you should have tried talking to her, you don't know her situation, she might have been a nice person etc. All true. I am in no way implying that women who cover their faces aren't full people with rich inner lives and agency. And agency is half the point, actually. Anyone who does this is deliberately making it harder for anyone to get to know them, they are deliberately wearing a inherently alienating piece of clothing that is also sending a clear political message about women's bodies, and I'm pissed off about the gaslighting that suggests the other party is to blame if they feel uncomfortable about this.
I mean, if I tried to have conversation with you while hiding my face behind my hands and peeking out between my fingers, it's not your fault if the conversation feels awkward and you find me hard to relate to. I am the one who is making communication between us difficult.