agree about the choice of Vronsky - he's flagged up from the start as being not completely "sound".
Interested that the likeness to Mdame B. has come up so soon.
Ages since I read AK but isn't there the scene on the train really early on where she goes into that v. deep, fugue state and it sort of indicates that the affair is so v. much about redressing something in her that isn't being answered in her life?
If so, it suggests that the affair between the two of them has a strong element of, very nearly, fantasy and the creation of an imaginary space - like MB.
And also what so many agony columns have to say about affairs in general.
And suggests that any affair she might have embarked upon, with any other person, would have been similarly doomed.
So, while the choice of Vronsky wasn't so great, it was a choice that fulfilled her deepest needs in embarking on an affair (he would play the game). she wouldn't have chosen a more "sensible" choice.
Agree she would have been better taking an OU course.