Princess Dolgorukaya and Arthur Thew

I have an Arthur THEW (don't know which of the Thews his parents were) who married Mariya Mikhailovna Princess Dolgorukaya in 1886 in St. Petersburg, Russia, USSR.
Have searched everywhere to find this Princess, and the only thing I could find even remotely resembling her is one of the daughters of a Russian Emperor who wasn't married to her mother. It's not much help, as the daughters aren't named. Ekaterina is the closest I can come to "maybe" her mother.
I'd like to put these two in the right place in my Tree, if anyone can help.