Given the more than 2 hour difference in arrival time your friend doesn’t need to spend all his/her time at Starbucks. He/she can explore the airport unless you have a lot of checked bags to lug around. It is easy to walk between all the terminals except Terminal 4 and there isn’t much at Terminal 4 anyway.

Terminal 3-Terminal 2(D)-Terminal 2(C)-Terminal 1(B)-Terminal 1(A) Terminal 4

There are a variety of stores and other eating establishments. As one exits the Terminal 3 corridor, there is a food court on the right and Starbucks is easily found, and there are plenty of seats. The only other Starbucks is just a small one on the upper level as you continue into Terminal 2. Much harder to spot.

The recheck area after Customs is straight ahead upon exit to the opposite side of the arrivals hall. One sees TAM first, and GOL and Azul are around behind it. Signage is good, so should be no problem. Coming from Terminal 2, your friend would need to go down one level and to the right.