Pinky rats are a mighty small meal for a ball python unless it's just out of the egg. It sounds to me like your little girl is hungry and crabby. I don't know about you, but when I get hungry I'm liable to snap for no reason too.
I'd try upping the size of her prey and see if that helps her settle down.
Then again, she may just be a little monster. One of mine is. She hatched that way. Doesn't matter how full she is, how warm or secure, she's just a little meanie butt. Snaps at anything that moves, even herself.
Gale