Understand completely. My pit gets scared when we pick up a folding chair, or even fold up his crate to move it. He starts barking, etc.
For the skateboard, you might need to buy one and just keep it in the house. Let her get used to it. Then start standing on it with your dog around.
Of course, it might just be the noise it makes on pavement that she is reacting too, so not sure.
