After a monologue where she admits that she doesn't regret making the choice to betray the MC at that time and sell herself to Kido. Though, she thinks that the right choice would've been to run away together. She just wanted to settle this (by killing MC) because her decision at that time derailed everything.
Bitch dies next chapter sadly she didn't suffer nearly enough yet still better than MC forgiving her in the LN according to some spoilers.
I'm gonna guess the Junpei she was fighting was a weak clone he made and he'll show up and two slap her, or he'll get back up with some regeneration and poison her.