Eldest Nye versus Suriel 1.0- the prior bearer of Suriel's mantle. In Valinhall. Since I feel location would be important there, maybe. When they give up a mantle does that make them more or less human?
Eldest Nye vs. Former Suriel
They're more human when they pass on the mantle, and they lose access to the former extent of their powers.
However, this only means that she would be unable to tear Valinhall apart with the force of her will alone. She'd still have his millennia of experience and skills, as well as his personal power.
However, she's scarred from killing people so she would likely stall, which the Eldest Nye would not do, and the Eldest has the backup of the entire House.
In the end, I don't think the Eldest has enough firepower to kill even a mortal Suriel. In the end, Suriel 1.0 would probably just find a method to cut through the Way and leave.