I think it's problematic that Faile apparently doesn't want that Perrin finds out her character's true toughness, although they are married for some time now. And all of Faile's helpers agreed to kill Masema; maybe Perrin would agree with it as well, if it is properly explained. Seems Faile either doesn't trust Perrin very much or feels that their relationship is actually too fragile to risk telling Perrin even such things like that she killed a mad man who just tried to murder Perrin.

Plus, as said, if Perrin reports back to Rand, he could certainly better explain that Masema had to die because of his evil deeds, than that he lost Masema again (I also don't see who should find the corpses in the middle of nowhere).