Who knows for sure in this case? It stands to reason that if facial and cranial features were doubled, possibly the brain is at least partially doubled as well. And given that the brain is all about making new connections, especially when you're young, it's a distinct possibility that this kid's eyes (all four of them) might be functional in the normal sense, or might become functional as she develops.
You realize, if she should get glasses, the other kids will call her "Eight eyes".
If both mouths work, and if they have separate vocal cords and both sets are controllable, suddenly you're confronted by the possibility that she could become the first person in history who could sing and accompany herself with her own second voice. Or speak two different languages, simultaneously, making her the world's best candidate as a translator.
If everything works, and she lives without complications, she could do some pretty amazing things.
CJ