The bridesmaid sits at a table dressed with a white cloth, draped in her own brushed-out auburn hair and gazing out of the picture with faraway hazel eyes. She holds a ring in her fingertips. Looking the painting up tonight, I learned that she's supposed to be practising the ritual of passing wedding cake through a wedding ring nine times, on St Agnes' Eve, to foresee her future husband. I always supposed she was at her dressing table, waiting for her hair to be dressed for the wedding. In any case, it's obvious from her dreaming face that she is imagining her own romantic future.
The bridesmaid's direct gaze and concentration capture the viewer's attention immediately, but her mind is a long way away from us and would be even if she knew that we are staring back at her. There's a gap between us that tempts me to guess the thoughts that fill it.
This essay at the Tate website, Sugar, Salt and Curdled Milk: Millais and the Synthetic Subject, is worth reading for a discussion of The Bridesmaid's place among Millais's other works. If you get a chance to visit the Fitzwilliam Museum, I would encourage that too.
Based on this prompt