My mother went to Ukraine on US passport several weeks ago, although she is clearly a Ukrainian citizen as well. Nobody asked her any question, except upon entry, a lady border guard verified my mother's surname in a perfect Russian language. My mother said "Да", and that was the end of conversation.My wife did that, and this was the conversation on our exit with the immigration officer (who was a lady very soviet looking, you know what I mean).
I was missing the entry stamp (they forgot, I didn't notice), so she was suspicious.
Then she asked my wife: "Kuda te doish"
My wife: "Tel Aviv"
Officer: "Pochimu Tel Aviv?"
My wife: "Prosta"
That was it. Kinda funny. And my wife US passport clearly shows as place of birth "Ukraine".
In your case, that lady should have known better to address your wife as "Vy", not "Ty" The biggest problem with Ukrainian border officers is that they pay a lot of attention where everyone is going even if the person is not Ukrainian citizen. In case with Ukrainian citizens, they often want to see the immigration documents for the destination country. Sometimes, I want to say "Mind your own business", but I know to keep my mouth shut