I had the same problem with my 280zx and I found the problem in a burnt wire in a plug behind the steering columb. The problem with this sort of thing is it could be a broken wire anywhere on the line to and from the lights, or it could be as simple as a bulb. Mine went with the tail lights, same thing with here? '83 300?? Must be an 84.
If she owns a 300ZX with the electronic dash, I had the same problem when I owned a 85 300ZX. What she needs to do is pretty simple. There is a small computer under the panel by the right knee. In most cases, the computer most be removed and the electrical connectors re-soldered. These unit are known for this problem. Over the years, the solder seems to crack, causing poor connections or shorts. Hope this helps.