Ooh, very interesting! Miriam's crystals also originated as a catalyst for a ritual twisted from one meant to summon benevolent beings to instead summon much nastier ones, so this will be a Fun(tm) reminder for her.

As for slowing down the growth, Miriam would offer the seals around her crystals as a template, as that's what they're designed for. Mass tattooing victims wouldn't be feasible, obviously, but maybe painted symbols or charms could contain enough sealing magic to hold the infection at bay? I see there's already a method to remove minor crystallization.