FWIW, Jeff Fredette was the top placing American in the ISDE on an '84 KDX 200, which is virtually identical to your bike.
For trail riding, my '84 was pretty much good to go from the factory. All it needed was stiffer fork springs and raising the fork oil to improve bottoming resistance. Besides the soft fork and the brakes, this was an awesome trail bike for its time.
Mine was very reliable until the stator went out. I also melted down the motor at an enduro when it got encased in mud. I went with a 240 kit, which gave great low end power but it would not rev out and it really killed the fuel mileage.
The '83 - '85 handles great and has decent power for a 200. I think it is a great bike for your GF, I hope she likes it!