The Sideshow heart tattoo is lower than the images above. There is something off with it's position. It appears to have been placed in a typical beauty spot position. The angle / left tilt also appears to have been over done, taking into account Harley's mouth is closed.
The fact remains, the tattoo is in a different place to the prototype. The factory messed up.
Possibly the logical reason could be, the factory added the tattoo after the front hair section was added.