I personally do not like Nadia, theres just something about her that I dislike.
Throughout most of season 4 she has had very little to do. She goes on missions but it basically just in the background, like Weiss and Dixon. She doesnt get alot of screen time but they play her off as an important character, seeing as she is Sydney's sister.
This episode finally gave her something to do. It revolved around her and made her alot more interesting. While I still am not a fan of hers I was happy to see Nadia be important to the show. She carried this episode and it was entertaining to watch.
I love how all the characters have the same horrible things happen in their lives. Sydney and Nadia were both betrayed and told that they were working for the government but they were actually working against it. Jack and Vaughn both had wives that were actually spies sent to marry them and get into the CIA. There are more but I just find this to be great plot development in the Alias world.