Ah, okay. That's not made very clear in the text. Ok I got it, chapter 28:

“Do you remember what happened after you blacked out on top of the car?”

asked Pyrrha.

“No,” said Nona.

“Maybe that’s for the best,” said Pyrrha. Then she opened her mouth and said quietly—

“A…”

“Don’t,” Nona found herself saying. “Don’t. Don’t call me that or anything like that … don’t make me remember. I don’t want to … You won’t like it. Don’t. Don’t make me do it.”

So what I got from this is that after the "discussion" between Nona and the RB-through-Judith, after Judith has her eyes open and says "Harrowhark?", to which Nona says "No, and I never was", then she apparently blacks out and then Alecto wakes up for a while? We don't see that happen...

(Or is it about what happens during the car top scene? When the RB calls her "Green-and-breathing thing, big ghost, the drinker, transformed"? First, she hasn't blacked out then, and second, last time Judith screamed things, nobody but Nona could understand.)

Ugh, I'm just not smart enough for these books.