@Geth270 Well, for this in particular it might mostly be a translation thing I suppose. The other characters might be doing stuff that warrants this treatment on their end as well, but it's not popularized like (or as easy as) this cutesy cat thing is, so maybe they just drop whatever it was. Perhaps this character was just ending sentences with "nya" the way some characters do with "desu," for example. For a dog version of that, it'd be a normal sentence ending with "wan" or something I think. May have seen that before, but it's certainly less common to see around here.
On the other hand, maybe the raws for this case really were more or less like this to begin with, bunch of weird cat based wordplay rather than just a tacked on "nya" here or there, I'm not really sure. More effort to look into than I feel like putting in, particularly since I'm mostly kidding with my reaction to it. I do kinda hate it, but I get why it's happening and can just roll my eyes at it, "Oh this again? Okay."
@Stalkerman Wasn't it probably the other summoned people? They might have left a message with her after he teleported away on his own, or perhaps they were captured or something and she was supposed to mention it since he obviously knew them.