Ooh, smoke is bad. My initial guess would be that the person your girlfriend lent the notebook to spilled something on or inside it. If that's the case, there's a very good chance it will need a motherboard replacement (which isn't cheap). Depending on how much the computer cost and how much it's worth to your girlfriend, you might be better off just buying a new computer entirely.
However, there's a possibility that there's just too much dust inside the case and it's causing the components to massively overheat. If I were you, my first step would be to open up the computer and clean out any dust buildup. After that, if you're still getting smoke, take a look to see if there is any discoloration or burn marks on the inside. Whatever is discolored or has burn marks will need to get replaced.