If they wanted a scandal, they shouldve just went ahead and said they’re in a relationship.
As you said, depending on who you date. The male MC is known to basically be a bish in the celebrity world so if the FMC dates him, she will be seen in the same way. This would ruin the image she made for herself/they made for her.
By becoming his best friend she is seen more like a tamer than someone who is into those kind of people and so may secretly be acting like him. As she is a woman having a reputation that's like his would be detrimental especially in Korea.
It would be better for her to keep her pure girl image who can even make the most cruel person alive want to be friendly with her.
Also them hating eachother is a private thing between themselves. They hated eachother so much that they struggle to act as proper best friends.
Arguing in public makes them seem more like friends but what if you see a couple constantly arguing? That has the connotation that they have a bad relationship.
By being besties instead of lovers they wouldn't have to deal with the break up scenario that would come after.
The break up would affect both their reputations even if they try to say they no longer liked eachother and that was it.
oh my god that Noa. swear cant bear to see a girl act so dumb for a guy