At one point during Biboo's Pokemon Legends Z-A stream towards the end when she is talking with Cece (timestamp pending), she receives a DM that causes her to gasp and get excited. Cece asks what that was about and Biboo says something along the lines of: she received great news that she can't reveal now. When Cece asks if it's something that she knows about, Biboo says no. (This is only from my memory, I can't find the moment right now. It wasn't clipped, and perhaps it was cut out from the VOD afterwards for secrecy's sake. Cece joined the stream sometime after 10:30:00)

My speculation is that Biboo was informed that someone she knows/recommended was accepted into hololive, likely via a DM from that individual. I don't know anything about Biboo's past pre-holo, but I guess that it would be someone she has interacted with before. I don't know if past-life info is allowed to be discussed here (is it "doxxing"?)

edit: Found the timestamps:

• (8:20:08 - 8:24:00) Raora leaves the stream, Biboo checks her messages, gasps, and gets stunned into silence.
• (10:49:16) The news Biboo received is something that even Cece doesn't know.