For starters I must admit that if it weren't for Kiara, we wouldn't have gotten 90% of the collabs so far since all the other girls are perfectly content with the mindset of "if the other girls want to collab, they'll DM me".
My hate comes exclusively with how she talks over people and drowns them out in collabs. She is so loud and obnoxious and unfunny that it makes trying to hear more quiet people like Ina impossible. That and she seems to try to make everything about her. Again, it's basically a very extroverted pattern, and it sucks because aside from maybe Nerissa no one else can wrangle her.

That's the biggest thing. It's fine if a collab has someone I don't watch or care for in it, so long as they aren't actively taking away from the people I do enjoy watching. Kiara is the only one who fits that bill. I don't enjoy Shiori for example, but she is fine in collabs because she lets other people talk.