Power and Prestige by Sarah L. McConkie

It is a truth universally acknowledged that a mage in possession of a vast fortune and refined magical abilities must be in want of a wife.

Yet High Mage Darkwood of Pemberley has no intention of marriage upon his arrival at Netherfield, especially not to the lowly Miss Cassia Retton. Accustomed to always getting his way, frustration reigns when his magical power against Cassia has no effect.
Cassia Retton puts little stake in inherited magical abilities until she travels to Rosings Park and everything changes. Perhaps it is the very land she stands on. Or is it the proximity to the awful High Mage Darkwood that brings out…something in her?
When Cassia’s family falls to ruin and she’s confronted with the scariest opposition of her life, will Cassia abandon what she’s always believed and summon her power within? And if she does, who will stand by her in the end?