Thanks, but I am not the poster who asked the question. But while we are chatting, do you have any ideas as to why Reeva would have opened the window in the bathroom but not turned on the light? Seems the odd way around to me.
As for her being too scared to talk, by OP`s version he was metres away and still screaming (his evidence is that after going quiet on reaching the bathroom he began to scream again, thinking the intruder was in the toilet). There is no logical reason why she would not have spoken at that point had this whole scenario been the misunderstanding he claims it to be. She cannot have thought that the intruder was between her and him as all there was separating them was a couple of metres of empty space. If his story to this point is true, there is absolutely no logical reason why she would not have said `Oscar it`s me`. None at all.
Sorry! I thought it was you. Oops!
Re the window... I don't know... Perhaps there was enough ambient light to see her way to the toilet and she had her phone with her anyway for a light source? If it was still quite warm, and she knew he was closing the patio doors, perhaps she just wanted bit of air coming through before she went to bed properly?
If she did think that pistorius and an intruder were heading her way, who knows what she would have thought in all the confusion? She could have thought pistorius was chasing an intruder down the passageway towards the bathroom. (there was plenty of room for another person to be in the bathroom than just pistorius) Or perhaps she thought pistorius was backing back towards the bathroom from the bedroom, being pursued by an intruder. If she wasn't sure which way, it would make sense to keep quiet and listen at the door to try and work out what exactly was going on.