That doesn't really help - it only slightly unbends the singular killer point (even if we assume she never delivers the killing stroke in any case but this one, she's still an active part of the murders), but makes 'the victim is sitting next to him' even worse - the victim was sitting next to the girl - HE was sitting behind the victim. A proper red herring should be either a complete lie, or else require only looking at the problem from a different perspective - this neither. It's presented as a true description of what's going on, but that only works if you seriously deform the meanings of the words used.