Sandre has 125 blight resistance. I don't know if that's an intentional value or not but as-is that means her health value increases upon receiving blight damage. The current way that the game displays this change in health is "(--X)," which is definitely unintentional. Picture features the Blight Orb power, I can confirm it also occurs for Withering Bolt. I'm pretty confident it works this way for all sources of blight damage but I'm not going to check.