Not that I give that possibility much credence…
My view is that it would be someone no more that 2 degrees away from her. For example, she had no problem asking someone directly to knock off her husband. That alone tells you that she is a seriously advanced sociopath. Who associates with sociopaths, that are not prey? Seems to me, that it is other sociopaths.
Now if you are asking more specifically “which” sociopaths in her small ruleless world, that is a good question. But again, based on her casual approach to looking for a killer to take out KH it would most likely be someone connected to her in some way, rather a random stranger.
Also, Seems to me her only reason for doing so would be for substantiating an alibi. Its not like she couldn't do it herself. But personally I think she did do it herself, and carefully worked out the alibis, etc so there would be “reasonable doubt” And in either case its very 1st degree, proving it is another matter.
Another point on this is that I think this was not only premeditated and planned carefully, but it was done primarily to hurt KH, Kyron was just the means to it. There was nothing worse she could do to hurt him. Unfortunately, there are many cases of sociopathic / narcissistic step parents (and sometimes parents) with that motive.
It seems very unlikely she handed it off to someone. But if she did, LE should be able to narrow that list of possibilities of her 1st and 2nd degree associations. And I would include her online associates in that list. A lot of people have an entire alternate life via the internet. If she didn’t have one, the list gets smaller. After 11 years, if anyone is on that list it ought to be very short.