It now appears that Maria Shirinkina will be making her debut as Cinderella at the Kennedy Center, as she is not appearing in the current Edinburgh run of the ballet...and neither is Somova (yikes!). Vishneva and Osmolkina each got two performances.
From a friend who attended the opening night of the Mariinsky's current 3-dy/4-performance run at the Edinburgh Festival, this was the casting as per the playbill. It likely yields good clues as to the casting of secondary roles at the Kennedy Center.
Cinderella & Prince: Vishneva with Kolb or Osmolkina with Sergeev (note: Vishneva not scheduled for DC)
Stepmother: Kondaurova or Iosifidi
Stepsister 'Skinny': Margarita Frolova at all performances
Stepsister 'Dumpy': Tatyana Bazhitova or Ekaterina Ivannikova
Fairy Tramp (Godmother): Elena Bazhenova at all performances
4 Season Fairies (all men in this version):
Spring - V. Tkachenko or Ilya Petrov or Alexander Fyodorov
Summer - Pimonov or Popov
Autumn - Zyuzin at all performances
Winter - Sitnikov at all performances
Dance Teachers couple - Nadezhda Batoeva at all performances, dancing with either Baimuradov or Zverev
AcIII Female Prostitutes group lead: Viktoria Brileva at all performances
Act III Male Prostitutes group lead: either Smekalov or Baimuradov
So there you have it -- Just as Fateev thrust Somova to dance her debut in a leading role (Juliet) at the start of a major int'l tour (London a couple of summers ago), so now Shirinkina will be dancing her first-ever Cinderella at the first night of the Kennedy Center run. Wow - not even giving her 2nd or 3rd night....she OPENS the run!
Very, very odd that Shirinkina isn't at least being given a 'trial chance' with the role in Edinburgh. "Lucky" Kennedy Center audience members will be the 'guinea pigs' for a ballerina's major debut at the opening night. We wish Shirinkina well.