Elena and Nadia are estranged. However, when Nadia was hospitalized, Elena came to visit. However, she brought a type of flower with her that Elena hated because she had been stung by a bee that had been hidden in one when they were younger. They got into a fight about it.
However, when trying to bring on Nadia's symptoms, Gregory House wanted to put Nadia under stress and told Martha M. Masters to goad them into a fight. Masters made a casual remark that was likely to bring on a fight, and, as expected, they started fighting again. Nadia kicked Elena out of the examination room. Masters went to tell her that the fight was her fault, but Elena was even more upset with Masters when she found out because it would just give Nadia one more fight to remember.
When Nadia took a turn for the worse and needed a new kidney, they realized that because they hadn't come to a diagnosis that she would never get approved by the transplant committee. The only possibility was a live donor transplant from a relative. House sent Masters to get the sister to agree and, after fumbling through the subject, Elena figured out what she wanted and agreed.
However, Dr. House was still curious. Nadia had told his team that the reason she didn't get along with her sister was that she was unable to do anything but objectively balance the bad things against the good things. Dr. House figured that as a kidney transplant was as far as anyone would go, that Nadia should feel the books were balanced. He instructed Robert Chase to take Nadia to see Elena after the transplant. He did and, after they exchanged some kind words, Nadia once again broke down and finally admitted to Dr. Chase that she couldn't help but concentrate on the bad things people had done to her.