>>65007858She didn't say why, but based on it only being in public and not in private and the fact that Ember seemed understanding of it my guess is that it's to do with Mio's audience. Mio is very conscious about losing regulars to other vtubers and has admitted that she unfortunately does get genuinely jealous about that sort of thing, and since Ember redebuted under Phase her content has definitely started to overlap with Mio's brand of parasocial GFE, so I imagine Mio is worried that if she associates with Ember too much publicly that it'll lead to people leaving her for Ember (and given how a significant part of Mio's fanbase seems to get a kick out of fucking with her over this kind of thing and rubbing it in her face to upset her I don't think that's completely unjustified).
Either way it doesn't seem like there's any bad blood between them at all so it's not really worth getting caught up on. As long as they're both happy there's no problem.
