My little sister used to cry in her sleep from growing pains
I second the magnesium.
I get restless legs and when they are bad, they can be really uncomfortable and even painfull.
I hope your poor poppet gets some relief soon. It's not nice

Eta, I know you said growing pains, but I wonder if they are restless legs?. Mine could be mistaken for growing pains if I didn't know what they were KWIM?