Apparently Sayu made Erina cry. No idea what she said though. Probably has to do with what Sayu said on Ustream, that Erina reminds a lot of her sister so she goes all out with being honest and possibly even mean without actually
meaning to.
So I found the story from 2ch over at H!O thanks to AlwaysAi.
道重さんに聞く9期の良いところはと言うテーマで 「ズッキはいつも笑っている」「フクちゃんは色が白くて 肌がモチモチ」フクちゃんは「フニャフニャしているみたいで嫌だ」って不満。「りほりほはとにかく可愛い」。 愛ちゃんも「さゆは子供好きなんだよね」って。 えりぽんの残して以上って話を終わらせる、5秒くらい沈黙 隣に座ってたがきさんが「まだ残っているよ」と言って まわりもつっこんだがえりぽん無言でだんだん堪え切れ なくなって泣き出す。慌ててさゆがその場で土下座、泣き 止まず舞台の正面に出てきて客席に向かって再度土下座 「2年半このキャラでやってきたの」と。愛ちゃんは慌てて側に駆け寄り、がきさんは「収録中だから涙を拭きなさい愛佳は「今まで溜まっていたんだよね」ってフォロー。そんなところ
Wow. Sayu, seriously.
Sayumi was asked about the good sides of the 9th gen members.
Sayumi: Zukki is always smiling. Fukuchan has beautiful white skin and it's all springy.
Fukuchan: I don't like it, it's all limp.
Sayumi: And Rihoriho is just really cute.
Aichan: Yeah, Sayu really like kids, right?
5 seconds of silence.
Gakisan: There's still one left.
The people around them starts picking on Sayumi too, while Erina remains silent and eventually can't take it anymore and starts crying. Sayumi gets heavily booed at.
Sayumi panics and kneels down to to apologize, Erina can't stop crying* and Sayumi goes out on the stage to apologize to the fans as well.
Sayumi: I've been going with this character for two and a half years now...
Aichan hurries to get Sayumi up to her feet.
Gakisan: We're in the middle of recording, stop crying.
Aika: She's been putting up with a lot until now, huh.
*- Could also mean that Sayu started crying and can't stop as well. I'm honestly not quite sure, it doesn't specifically say.
Seriously. I wanna see this. Sadly we probably won't get to though.
According to fans at twitter, Sayu seemed really depressed after this happened. She most likely felt quite awful.