Russian episodes aren't shot and aired in the same order as their American analogues. Since the beginning of the sixth season, all episodes are brand new.
The production of The Nanny (1993) noticed that once when Fran was engaged, ratings went downhill. In this series, after the same episode, Vika wakes up understanding that that episode was only a dream... and the same old pattern goes on.
After the second season, Gulya Nizhinskaya and the rest of the crew had a conflict (although it is impossible to know its exact nature, because the story is told differently by the actress and the production crew), she left and Vika's friend was recast. But to avoid fans taking it badly, the newly-recast friend was made a new character. That's why in the beginning Vera is Vika's best friend, but when her other best friend Galya resurfaces, Vera is nowhere to be found.