My first son got his first pillow at 18 mths when he moved into his new "big boy" bed. He is now 2 1/1 and NEVER uses it, prefers face down on the mattress (still freaks me out to see him like that, I always think he's suffocated himself).
My second son is just now 1 year old and he stuffs his blankets under his body, and I'm considering getting him a pillow in the next few months. My only concern is with him being in the crib, that it will give him that extra few inches of height to be able to fall over the rail. He is 32 1/2 inches as it is, so on the tall side.
I believe it's safe sleeping wise for him now, but am still concerned about the other issue.
I think that at this point, it's a personal choice, you know your child and if you feel like she's able to move her head around if she is having a hard time breathing in one position, than I say go ahead and get her one.
K.