May 6th, 2011.
This story is what I think Kara did when she left the show. I do not own any of the characters from Smallville or Superman or Supergirl. They belong to the CW and DC comics.
Kara and Oliver had just shot their arrows to open the gate to get the Bow of Orion. The door slowly opened with a bright light. They headed to the gate as it was still opening. Oliver stared in wonder. "Nice shooting, partner," he told Kara. "Thanks," she replied with a smile. As Kara headed toward the gate, she heard a high pitched screeching noise. "Ugh", she said holding her head. Oliver looked worried. "Kara, are you alright?", he asked her. "Whats wrong, is this another trap?" "It's Jor-El", she replied, " I have to leave." She handed Oliver his bow and told him "You have to retrieve the bow and deliver it to Clark. I'm trusting you now." She then supersped out of the cave.
Kara arrived at the Fortress of Solitude. "Jor-El," she asked, " Why would you call me back when I almost had the bow?" The voice of Jor-El answered, "The bow is Kal-Els destiny, not yours." "You told me to protect Kal-El", Kara said, "Why would you interfere when I was so close to finishing what you told me to do?" "I believe you care about Kal-El and wish to help him," Jor-El replied, "but ultimately this battle must be his. That is why I've called you here to make a choice." "A choice?", she asked. "There are two paths laid out before you, Kara. You can leave Earth now and allow Kal-El to embrace his destiny or you can stay and help him risk the future of this planet," he said. "Kal-El and I have fought Darkseid together before.", Kara said. "You involved Kal-El against my wishes," he replied, "He was too weak then and he was almost overcome by darkness. You have grown strong. Your will is no longer at the mercy of my command. You will need that strength to forge your own path. It is in your hands to choose." Kara was disgusted. "You want me to just walk away?", she asked. "Kara," Jor-El said, "Your own destiny is written. It is in another place and time but this is Kal-Els battle and he must fight alone. Even though a time will come when he turns away from me, in the end he will make the right decision. He is ready. This is his time." "He's the only family I have left," Kara said, "I have to at least warn him." Jor-El replied, "Sometimes the greatest sacrifice a person can make is to give up what they hold the most dear."
Meanwhile, Granny Goodness destroyed the bow when Oliver reached for it, the Toyman was controlling Stargirl, then Lois and he met with his gang, but Clark saved Lois and he went to Toyman and destroyed his phone and tells him he will always be there to stop him. Then he went to Jor-El and shut down the Fortress. Oliver got gold kryptonite and made a ring for Clark which would take Clark's powers away for good. As Lois talked to Clark about him having a big heart, Kara was hovering outside Watchtower. She was holding a Legion ring and crying. "Good luck, Clark," she said, then she slid the ring on her finger and disappeared. Clark continued to be the Blur and Lois and Clark canceled the wedding but then they worked it out. Clark stopped Apokolips from taking over the world, Lex is resurrected, Lois and Clark didn't get married due to Apokolips, Clark learned to fly, Jor-El awoke and Clark became Superman. He didn't know his cousin was gone. She WOULD be back soon but where she is at it will seem like a long time.