You're probably better off either asking in english, or at least actually quoting the wiki rather than… something about a dinner scene?
I assume you mean the line "Requires the player to have scene the event where she is eating by herself" - which is a spelling mistake, it's supposed to say "Requires the player to have seen the event where she is eating by herself"
Sometimes, you can find Bianca eating by herself in one of the bars. You have to have interacted with her while she was eating in one of the bars to ask her about her family.