Just to show you, Yozza, this was taken with either the FA77 or DA*55 at f2.2 in low light conditions, so there was very little margin for error.
While nice, how much better would it have been if I'd noticed that the ring is not in the same plane as the eyes and the flowers?
I could have focused on the flowers instead of the eyes, and narrowed down a bit to extend the DoF to the ring in front and the eyes at the back, or I could have asked for the model to alter her pose so the ring finger was back and across, at the same level as the flowers. Alternatively, she could have rotated her body a bit and pushed/turned her face forward.
The problem is no different to you photographing three people, actually.