It makes no sense at all for Asuna to be an illusion.
The illusions already had Touta and were dragging him down. The Mage of the Beginning had him defeated. It'd have been completely stupid and pointless from her to summon an Asuna to save him, then revive Evangeline, so they could kick her butt afterwards. So she could torture him more, when she'd already effectively broken him, to the point he was telling himself it all was hopeless? I mean, that'd be beyond Cartoon Cobra Commander levels of villain idiocy. Heinz Doofenshmirtz would call that a stupidly contrived selfdefeating plan.