Man, what a cheap way out of that mess. And a bit stupid too. Why not just have her forget the past few days? It could be chalked up to stress. If she doesn't remember him at all the gang at school will definitely become suspicious that something strange is happening. And even if she moves away or whatever they're friends, so it's not like they suddenly won't talk to her anymore. I also can't see him abandoning the school and his sister as she is pretty much the most important person to him.
I don't really know what to think of the crazy guy with the new geass. At first I thought the geass must have something to do with Britannia, like a new weapon they were developing. But it doesn't look like Mao has anything to do with that government. So CC's been running around Geassing people before she met Lelouche, huh? Looks like her motivation might be completely separate from the whole Brittania/11 conflict. But why did they have her then? What is she get out of this I wonder? Maybe Lelouche will finally start questioning her some more. I thought it was something of a plot hole that he trusted this bizarre chick that he knows nothing about anyways.
As an aside, it's nice to see a series where people actually don't know what will happen next for a change.