That’s a possibility but I don’t think it’s a smart move. But considering hybe behavior so far they may be really that dumb.
First the person that can sue Eunsoo on spreading rumor is Garam. And even if Hybe sue on her behalf, at most it would be a libel case. However that happened over 4 years ago - how are they going to prove Eunsoo was the one who spread the rumors? And most importantly what financial damage did a 13 year old Garam incurred then? That’s a losing case and just dig a bigger hole in public opinion for hybe. Idk that smart at all.
When I say Hybe it's Hybe/Garam. Of course if they sue Eunseo for defamation it will be in the name of garam. However, it's not just the loss of money that justifies defamation. But more because it tarnishes someone's image and would have led to Garam being harassed in a chat group. And if it's true I think it won't be difficult to prove with the testimonies of the people involved and the focus group. Nothing disappears on the internet.