...this is kinda vile.
She asks Ryogo to think about the boyfriend label just to get under his skin and have him consider what it means. Ryogo accepts, and she flips the script on him and decides to be free, making him anxious, and then proceeds to "cheat" on him (I know it isn't since they're not really a couple). If you've moved on...just move out.
Why are josei like this.