you have to understand, hiring is at the managers discretion. and unfortnately, a bad past experience can colour preferences in the future. It's happened to me before-- I was commuting to a job outside of the city, and I'd occassionally want to work from home (because of assignments, or bad road conditions in whether, whatever). My boss took forever to convince that i was actually going to work, and only requested to do this because it was actually moer time efficient (like if I had meetings in town, there was no point commuting to the office only to have to come back into the city), or the roads were really truely dangerous. Why? not because of anythign I'd done, but because a past employee had taken advantage of this, 'working from home' whenever she wanted a day off.

So perhaps this person, questioning whether or not you could move around and do the work in your abaya and niquab, had had a previous bad experience: maybe a past employee hadn't had these specially cut abayas you speak of, or it really did become a problem, not just the dress, but refusing to do certain things or taking too many breaks throughought the day on top of breaks for prayers or whatever. It might not have been about you, or about your religion, but about one person who coloured the managers perception.