Why?
Yui is probably the most advanced AI ever written in this setting, and even if Kayaba abandoned her, she's been continuing to develop since Kirito and Asuna "adopted" her. Kirito has even been toying with man-machine interfaces, and Asuna is of course incredibly wealthy and probably owns all of Kayaba's old technology and programming assets.
That was one of the most plausible things that happened this episode.
Put Yui in a cellphone, link the cellphone up to the connected networks, and there you go. It's the Internet of Things, controlled by an AI solely developed to interpret natural human speech and emotions.
Compare that to, "I can use metal swords if they are precisely no greater than my preferred weapon type (LOL, it wouldn't work for what you like to use Kirito!), can slide them into my unique drop sniper rifle, and it is conveniently made of the strongest metal in the game that can't be burned through with you laser sword, and even though my partner is creeping on Sinon in her apartment that she can just tell you the address of, I can't be stopped because you don't know the handle I used in another game!"
I think it is pretty clear which developments break suspension of disbelief.