No, you can't shoot them. You would get major jail time, 25 years +.Legally, If someone were to do this to my car can I shoot them? Or do I have to be in danger of physical harm myself to use lethal force?
If you stepped in between the car and person and she started swinging, then you could defend yourself and you would have a reasonable defense that you were in danger of death and serious physical injury.
You don't really wanted to get into major trouble so it would be best to just call the cops and get her arrested for felony vandalism and sue for damages on top of that. Just videotape the action on a camera phone or video camera if you have one, and it would be an open and shut case.