Where did you get her?
I had a similar one from Cackle Hatchery some years ago. Actually two: one was missing half a toe (looked like it hatched that way), and another had two nails on one toe, sticking out to two sides.
And this thread has a post by someone with a Spitzhauben from Cackle Hatchery, that also has a weird little extra toenail:
https://www.backyardchickens.com/threads/spitzhaubens.164012/page-226#post-27554328
Plus another one a bit later in the thread:
https://www.backyardchickens.com/threads/spitzhaubens.164012/page-226#post-27554788
I'm seeing a bit of a pattern here, but I don't know if the problem is with Spitzhaubens in general, or just ones from Cackle Hatchery, or if it also happens in other kinds of chickens but I'm not noticing those posts.