As a foot fetish artist, I can assure you she does have normal feet.
It's simply a perspective thing; her hallux / big toe is bent back in that angle, hidden behind her second toe.
Oligodactyly doesn't generally only affect one hand / foot and show zero signs of deformation on the others. You can see her hands frequently, which are fine, and in her good ending, she's on top of Vincent in bed, and she's barefoot. Her right foot is completely normal.
So, yeah. She's not an eight-toed mutant.