In the old DCU Princess Komand'r hated her younger sister Koriand'r. She betrayed their people and forced her parents to sell her younger sibling into slavery. That's not what happened here and well the changes make sense because their not the same people. Their parents died (not said how) leaving Komand'r as queen at a very young age as well as a surrogate parent to Kori (unknown if their brother Ryand'r exists.) They loved each other because none of the problems their previous incarnations had carried over. But Komand'r is still the leader and that meant putting her people first. So to ensure her planets' survival she allowed Kori to be sold into slavery. After freeing herself Kori wants to act on her feeling betrayal only to find Komand'r overjoyed to see her again. They try and fail to repair their relationship leading to them separating.
Years later Kori returns with her friends to free her home world. Face to face with her sister she asks for them to be left alone. No one thinks it's a good idea but comply to her wishes. I knew what Lobdell was planning based on interviews but it was still hard to believe. Seeing them interact makes the retcon work and makes any future fights more heartbreaking.
Why I like it: I've read a good amount of the old Blackfire/Starfire feud pre-Flashpoint. Sometimes it was good but it grew stale over time. Once Komand'r was made queen and Kori couldn't really fight her without coming off petty to others. They were kind of at a stalemate where they couldn't really do anything to the other. They weren't really sisters, they never cared about each other that deeply. This change makes sense and gives weight to what happened between them. While Komand'r isn't the villain in this (nor is she ever actually called Blackfire) the potential is still there. Because as much as she loves her sister she knows that if she has to chose between their people and her then she'll have to lose Kori again.
Personally I never felt the previous take of Kori forgiving their parents for giving her up worked for the character. Yes she's a loving person but she also has a bad temper. Seeing the conflict would have added more depth which I'm pleased to see here. To see that sense of hurt and betrayal created a rift worked. Just like Kori realizing that she had finally come to a point where she could not only forgive Komand'r but understand why she made the choice.