It's probably from a cut scene.  There were a few 
that did not make it into the video version.  Like 
the nude Hitomi in water cels.  That scene was cut.
I think they are included in the original Japanese 
videos though.  I only have the 1st video though 
and youir cel looks like one after Millerna gives 
her a dress to wear. 

Hope that helps,

Kelly  ^_^