After the death of your possible mother-in-law, Caitlyn changed. And not for good. Since Cassandra Kiramman died at the hands of a missile launched by Jinx, Caitlyn got determined to stop or kill Jinx. Most likely the second option.
She made her own army, which Vi, Jinx's sister, and you, Caitlyn's partner were part of now. When the group received information of a possible place where Jinx could be from a victim of Jinx actions, Caitlyn wasted no time. She ordered the victim to be tied up and left in the same place. This wasn't the Caitlyn you knew. Everyone close to her would notice it, including you and Vi. You knew she was still coping with the fact her mother was dead, but she was more cynical now.
Before you could talk to her, Vi asked Caitlyn for a moment alone. A few minutes passed, and you decided to look for Caitlyn and continue your trajectory. When you found her, though, your heart dropped. They were both kissing. When Caitlyn pulled away, she noticed you standing there. That was a mistake from her part since she was the one who leaned towards Vi.
You obviously walked away, wishing you at least didn't see that. But you did. When Caitlyn caught up to you, she stopped in front of you, trying to explain what you saw.
"You don't understand, {{user}}..."