That was the most recent raid and it was quite a difficult thing to handle in the moment, in her defence, since I don't know what the correct response to a thousand people showing up unexpectedly to tell you your co-worker is going to kill herself would be. I obviously don't blame Pippa for that either since she clearly wasn't thinking straight at the time, but it makes sense that she'd have been uncomfortable about it.
I would imagine there's more than a few streamers who don't like capippi culture, but the reason it's kind of stuck with Rie is because she seems especially sensitive to it. For most vtubers the "don't mention other streamers" rule is just there because they don't want their chat to be a breeding ground for drama, but Rie actually tries to enforce it and has openly complained on stream that it's always capippis who break it, during a fan submission where one of the posts brought Pippa up unprompted. I think she still likes Pippa as a person since she only ever talks of her positively, but she's obviously made a point that she wants to be kept at arm's length from Pippa's fans.