All the comments under the VOD say she's going so I just assumed she talked about it. Her tweet is vague enough to be able to be read both ways.
Then again, Vivi talked about Doki a lot more than I thought she would (and thought she could honestly), so at the same time I thought they might have had some chats away from managers eyes, which is how she would have known that Doki probably couldn't go.
A Mystery so far, but what I will definitely say is that the way the two Team Shine tubers talked about having to bow out definitely makes it seem like logistics issues rather than perms.