Can someone please explain to me what the point of this scene was? It seemed very out of character for Do Min Joon to pay any attention to a female flirting with him. This scene made me feel like he was wavering and i did not like that.

A very belated reply, but Suzy's cameo appearance was in reference to her character 'Go Hye Mi' and Kim Soo-hyun's character 'Song Sam Dong' in the kdrama 'Dream High'.

They were the main leads and paired couple, so that's why Go Hye Mi mentioned that Do Mi Joon looks like her ex, Sam Dong (because they were both played by Kim Soo Hyun).