Board Thread:General Discussion/@comment-131.191.42.13-20151212230228/@comment-1173941-20160110025714

Don't be silly. Why would Kayaba create her only to lock her up? Clearly she was not created for the players that were trapped in SAO. She was created for a more general purpose, in maintaining a player's mental health, because they didn't know the long term effects of constantly playing a VR game.

Sword Art Online becoming a Death Game, and Yui's creation, are unrelated. The sort of mental health she was meant to handle was generally things outside the scope of "I'm trapped in this world, and want to get out". More along the lines of "my parents are pushing me too hard in school," or "I think my boyfriend is cheating on me", or any unforeseen issue that might pop up from constantly playing a VR game, that wasn't known before.

In that case, it's likely she at least had a trial run during the beta.