It's just Rulue and Schezo, being... Rulue and Schezo. That's it. There are in a puyo battle and apparently Arle immediately assumes the worst, simply
because other people problems and battles don't matter, and Arle can't deal with conflict anymore. I mean seriously, everytime she has to deal with something she acts all put out at best.
It seems that Arle does not talk about Rulue or any of her old friends, if you can call them friends. Arle and Rulue aren't freinds anymore now that she's got Amitie and Ringo, because Arle actually waits to the last minute to tell anyone about Rulue. In *every* description of Rulue is Amitie's novels, is "someone who is beautiful, but very scary when they are angry" and generally freaks out at Rulue's presence everytime Rulue does anything.
Arle knew she was going to have to get Rulue involved at some point and Rulue was the closet thing Arle actually *has* to a friend, and it's sounds like it's the very first time she brought Rulue up. What even worse is that Amitie and Ringo met Rulue in Puyo 7 (unless you count 15th).