I love it! It goes really well with Theodore, and gives her lots of nickname options. Plus she'll be able to read the Anastasia books when she's older. Those are great.
Are you Greek too? I'm half. My parents almost named me Anastasia! I was wondering which pronunciation you're using. I like the Greek way, but you're right most people aren't familiar with it.
No, not Greek at all! I just always loved Theodore. And Anastasia is so beautiful, no matter how it's said, IMO. I was a little worried that doing Theodore, Anastasia and say Margaret or William would be weird and perhaps it is, but I think Teddy, Annie/Ana and Maggie/Will work just fine.