L.C.
I think I'd get her involved in activities she enjoys. If she likes soccer, sign her up for a soccer team. If she likes reading, sign her up for a book group at the library. She needs to meet kids that enjoy the the same things. How about karate or girl scouts? How about gymnastics or ceramics? Let her try things that are out of her comfort zone - you might find she might not be great at something, but really enjoys it.
The other kids need to see her as just another kid -- not the smart kid. Sure she's bright and has excellent verbal skills, but when it comes right down to it, she's a 3rd grade girl.
As for Christian friends - that sounds very closed minded - there are very nice Jewish or Hindu children who also make really nice friends. Don't forget that church is full of sinners. The kids that seem so nice in church might not seem so nice if you saw how they act on the playground. I've met some atheists that are far nicer and far more honest people than some so called Christians.
YMMV
LBC