Yes, hobble her, or tie her leg/legs back so she cant kick the calf. Unfortunately you have to do this for the first little bit. After a week or two if she is still kicking, then she is probably helpless. The calf should be strong enough by then that he will just be able to steal from her and other cows. It is good that he is very aggressive and strong. Let him have at her when she is hobbled well and tied up. It has been very rare that one of our cows kicks all the time, regardless. Usually if the calf is good and healthy, we will just let them into a corral/paddock and moniter them for a couple days. If he is doing ok, then let em out to pasture. The darn cow should be able to figure it out after a couple weeks that the calf is hers!