I was doing the challenge event Rare-7 stage with Marie-Thérèse as the lone boss. I noticed that if she is turned into a zombie, her hit box is changed so that column five (counting from the left) no longer hits her. The tiles pass through without generating mana or dealing damage. Columns three and four still hit her as expected. While she is in her normal form, all three columns hit her, as expected.
P.S. the animation where she drops her loot before transforming is awkward.
P.P.S. sorry for the slow play - I wanted to make sure that I replicated the right thing for the video.
This bug may be related, or share the same cause: Marie Therese zombie bug – “Nearby” Splash Damage Doesn’t Hit Adjacent Enemies