This is maybe intentional? Likewise, Lizuca at the Sanctuary of the Coming Dawn cannot remove level drain. When you ask for an NPC healer to "cleanse you of disease and illness", they just cast Remove Disease, which also cures ability score damage, but doesn't cure level drain. The only spell that fixes level drain is Restoration, and I'm only aware of 2-3ish NPCs that cast that one.
It would be nice if more NPCs could cure level drain, since usually you need to sprint all the way to Western Barovia, even if you're in eg. Dementlieu. But iirc it's a design decision to encourage seeking out player clerics.