When AOA's bullying scandal hit Seolhyun stayed silent, despite people speculating that she was Jimin's "partner in crime" and Mina branding her a bystander. She was cancelled to the max, with cfs deals disappearing, and speculations and rumors about her were flying everywhere, yet she never "shared her side of the story" or commented on the situation, just let some time pass and quietly started posting to instagram again.
Now that Mina is running her mouth, she's losing credibility, the tide is turning in Seolhyun's favor, as people want their pretty unnie back on TV.
Compare this to Jimin, who posted messy statements on instagram calling Mina a liar, but not actually contradicting any of Mina's claims, and you have a reputation that's unsalvageable
Silence is obviously the way to go... Mina and Jimin released messy statements = now their reputation is in the trash. Seolhyun stayed silent = people are warming up to her again