What is a good gift idea for a friend that is a girl that will be going on vacation to Peru?

A book about Peru, like Lonely Planet.

It depends on what time of year she is going and what part of Peru she is going to. If she is going to the mountains sometime between now and March, it is the rainy season (in the mountains, but not in Lima...there it is hot and sunny). A rain poncho she can fold up and carry in her pack would be helpful. There are often sudden rain showers in the afternoon and evening.

a GPS that will help her go around in Peru, there are small ones and used one, actually i have one i can seel you too, so email me if you are interested.

She would need to download Peru's map and she can put that in her pocket and write down teh address and the GPS will take her there.

Some new shoes/sandals that are very comfortable.