Much is made of Lizzie beheading her victims. But the location of the severed heads is never revealed or mentioned. Ryan looks at a couple of "loose" wax heads in the wax museum, but it's never shown that those are the victims' heads.
The Lizzie killer apparently leaves one, maybe two witnesses for her onscreen killings. However, they are never mentioned again or referenced.
When Lizzie attacks the shop, it's revealed that she is actually Marie. But earlier in the episode, Lizzie was shown killing her victims while Marie is at the wax museum, suffering from one of her "spells". So it's not clear if Marie is Lizzie, or they're two separate beings.