That is, I find the idea that, nearly immediately following her rescue by Perrin after previously being kidnapped, she managed to slip out of camp long enough to pull off this assassination without Perrin knowing about it.

Let's see, wife is off without enough guards, gets kidnapped, husband spends the better part of 2 months getting her back, leaves quickly in the face of more enemies showing up, still has a maniac who tried to have him killed somewhere in the vicinity and now wife slips away AGAIN to pull off this assassination.

I am not calling Perrin a stalker or anything, but let's face it, if they were invented he would have a tracking device surgically implanted into his wife by now.