I don't know, Nerf. I regularly swing towards him thinking, at first, that it was an intruder, to wondering if the row suggestion holds water. Both sides, to my mind, seem possible, and which seems more probable changes from day to day.
There are huge chunks that seem improbable to me. Fussing with the jeans to make the room pitch black because, despite the fact that he's slept so soundly he didn't hear her go and get a snack, he suddenly can't sleep with that tiny amount of light. Without having even tried. I think it's improbable that he carried his gun, the gun that apparently went off without him even thinking about it, into the bedroom, across the bed, with him while he opened the curtains and went onto the balcony, back into the bedroom to find his legs, during which he had to find his socks in the dark... all of which happened without this hair-trigger going off accidentally again.
Those, to me, are the really implausible bits of his story.
However, I can't make the leap to 'he must have known it was Reeva' just from that.
That's why I keep getting stuck on what he thought when he fired for the first time, and whether the situation changed when he then shot three more times.
I think it's possible (though entirely conjecture) that he though it was an intruder right up until the moment he shot first, but by the time he'd finished shooting, he'd already realised his terrible mistake. I think that's possible.
But that's just my personal thoughts, and I'm not entirely convinced that I'm not missing out massive chunks of evidence to make it fit. Particularly with the other big vaguely implausible one - she got up, got out of the bed and went into the toilet without talking to him, and without him noticing she was not in the room any more. And there are the witnesses who heard voices before the shooting.
So I'm still well and truly on the fence when it comes to whether or not he knew it was her.