Honestly Eris fucking Taiga-ing Rudeus is pretty dumb. She had to have known that he would still go off on his own and do shit even if she wasn't in the party. And even if it was because she could become a lot stronger a lot faster if she was alone, it would take years for her and in that time...
As soon as Rudy fucking said that I was like "Paul's totally gonna fucking kill him" and he just did. (Except not actually and mf got plot armor as the MC.)