I thought it was made pretty much explicit by the fact that she was amnesiac when the gang of thugs burst into Ougi's place to rape/kill her, then was back to herself by the time she'd finished dispatching them.
I mean, when do you logically take a break in the story to point something like that out, anyway? Unlike Lelouch's little romp with Suzaku, it wasn't one of the great mysteries of the first season. Not even a minor one, really, given that most viewers will arrive at a logical conclusion based on what they've already seen.
Post-traumatic amnesia passes with time in any case, although real-life PTA usually results in the loss of only a small portion of memory, or the loss of cognitive functions after the fact; cases of global amnesia like Viletta's are very rare outside of fiction. On the other hand, it would make even less sense to stop the story and say "enough time had passed for my brain to recover/I suddenly got better."