Separates
The wedding was at three in the afternoon in January and the walk between the two buildings was nine minutes long. That is the whole brief.
So the dress is a coat, cut like a coat, with real pockets and a lapel that is hand-picked along the edge. Under it is a slip in the same ivory, which is what she wore for the rest of the evening once the coat came off.
Wool is unfashionable for a wedding and is the only cloth that would have let her enjoy the day.