Ah okay, so this is indeed not Kitty - but the woman next to Serge is definitely Grand Duchess Ella!
I have never heard the name Sophie de passavant..........
interesting
Well, I'll look one more time to my sources about Ella's presence in Bosenon in 1895. Not sure that's her.
I've looked through the sources with the chronology of the Grand Ducal pair's travels and the fact is that:
August 21 1895 GD Sergei left for Bosenon alone as his wife had to finish her cure in Franzensbad. He was visiting Bosenon till the end of August, then left for Italy - alone with his ADC - and only in mid-September he and Elizaveta meet in Darmstadt.
That photo was taken in August, before Sandra's engagement to Ernst von Hohenlohe. There is a family photo of newly engaged couple with Duchess Marie and GD Pavel, M-lle Passavant and others, where Duchess Marie is in the same dress as in the photo we speak about. I don't think that she would wear the same dress a year after if we imagine that the date of the photo is 1896 (when Ella indeed visited Bosenon with her husband).
So, I still don't think that's Ella in the photo.