I'm sorry, but this is... I don't even have words how bizarre this is. Xp spending haven't really been story driven at all, you are inventing it whole cloth, and in a way that doesn't make sense. Arawn is the god of the dead, Lydia is an exigent of death. Dealing with undead magics of ghosts is what should be coming first for her. Her primary core feature, as well as her father's mantle, is about countering ghosts. I am really sorry, but the only way I can describe this reasoning is "stupid". It's inventing stuff with no badis to buy something deeply suboptimal despite optimal choice being more narratively logical.
I am frankly baffled by this explanation.