What about making a ball out of rope? You can get hemp rope or even make it yourself if you’ve got a lot of time to spare. You can have a rubber core so it’s squishy and a rope shell to protect it, if she wants a squishy ball. Or make it completely out of rope so it’s more durable but then it depends if she would like it.
I’ve been told that as long as there’s pain that shouldn’t be there, don’t do that until the pain is gone. I’d still move the affected muscles a bit to see if it hurts but don’t overdo it. Use smaller weights or even without weights and see if the situation improves in a few days or so.