Has she been like this since birth? Babies get use to being in the womb where it is snug and warm and once their out the snugness goes away. Have you tried wrapping her up real tight in a blanket with all body parts except for her head tucked away, I know that works sometimes. They also have a bear out that plays sounds to resemble inside the womb. To help sooth your baby. If she just started doing this there might be something wrong with her that isn't visible to the eye.