It's weird how Mrs Coulter looked almost ridiculous
in "normal" clothes when she dressed to fit in with our world, when Ruth Wilson probably dresses more like that in her day to day life, than she does like Mrs Coulter.
I wonder if they purposely chose clothes which don't really suit her, to make her look not quite right.
(As an aside, while she might have looked rather formal, I don't think her own outfit was THAT out of place, especially in Oxford)