You said you are happy overall with your employees performance. That being said if she shows up on time everday, completes her duties and treats other employees with respect then is there really an issue? A little internet surfing seems trivial to me (just my opinion). If her web browsing starts affecting her job and completing tasks in the requested time, well that is a whole different story.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne