In other answers RJ actually always carefully uses "he or she", if he wants to leave the gender open.

For example:
"It is very unlikely that a channeler forcibly turned to the Shadow could find a way back to the Light unaided. For one reason, by virtue of the twisting he or she had undergone, it is very unlikely that he or she would have any desire to do so."

Or:
'For the rest (aside from Ishamael), who spend those thousands of years in a dreamless sleep, the language spoken "here and now" was derived from the Old Tongue. I've heard the analogy used of a well-educated, highly intelligent citizen of ancient Rome needing to learn modern Italian. It would hardly be a slam-dunk, but he or she would have the roots of the language already. In the case of the Forsaken, the task is actually easier than that of the ancient Roman, since modern Italian is a more complex language than Latin, while the Old Tongue, as I have said time and again, is more complex and nuanced than the language of "today." '

Or:
'Yes, a woman would also see through the eyes of her ancestors, at least in the “forest of crystal spires” ter’angreal, and she, too, would live the history of the Aiel, in effect. Someone who wasn’t Aiel could wander through those spires forever and never see a thing except the spires. He or she might think it was a monument, or maybe a work of art." '

Or:
"That helps me to find where the error is located, if there is one. For example, somebody said that he or she found Verin channeling saidin in Lord of Chaos. Check as I can, I cannot find that anywhere in the book, and neither can my assistant Maria. Maybe it is there, but I can’t find it."

Or:
"Now as to communications and the lack thereof, these things are not commentaries on any sort of technologies. They are a commentary on the human navel. Do you really know anybody who actually tells everything he or she knows to everybody? Even when they really need to know?"

Thus it's safe to assume that in that answer about Asmo, RJ unconsiously - maybe because of his apparent agitation - slipped and used just "here he is", because he of course pictures the killer (most likely Slayer) as a man in his mind and didn't even think about including "or she" in this situation. Therefore a Forsaken like Graendal is per se ruled out (of course there are also many other reasons, which speak against her).