Ok, did more reading up on the leyline rules. I should and will codify them on the wiki with a few changes I've made as soon as I can.
But for now, to answer your question.
You can do an opposed CL check as Niyut did before or...PFSRD wrote:Dispel magic and similar effects can break a creature’s attunement to a ley line; the caster attempting to break the attunement must succeed at a caster level check with a DC equal to 11 + the caster level of the ley line.
The leyline of Death at this location has a Caster Level of 15. So, the DC is 26 to dispel her connection. This doesn't take control, but it could disrupt or at least pause the ritual as the leyline connection is required for the ritual.
My apologies, as I just realized this requirement wasn't in the ritual entry on the wiki. I've updated it.
Oh! That's important!Apparently, the ley-line attunement is necessary for this ritual.