I'd bet dollars to donuts that Joohyun thinks they're already dating because they were watching a romantic movie together and started making out. She isn't confessing because she thinks they're past that stage, and Ahyoung's attempts to confess are getting stymied because every time she throws something out there, Joohyun is just like "Ah, my GF is showing me affection!" and she isn't reading it as something she needs to respond to directly.
I'd bet dollars to donuts that Joohyun thinks they're already dating because they were watching a romantic movie together and started making out. She isn't confessing because she thinks they're past that stage, and Ahyoung's attempts to confess are getting stymied because every time she throws something out there, Joohyun is just like "Ah, my GF is showing me affection!" and she isn't reading it as something she needs to respond to directly.