Turn them into the window, not the room

Find the brightest window. Turn the subject 45 degrees toward it so one cheek is lit and the far cheek falls off. Do not add a flash yet. Take one frame, then take a step left. If the catchlights disappear, you rotated too far. On a wedding morning this saves you when the room is yellow tungsten and the window is daylight. Expose for the face, let the room go a little dark.