If your friend has been enrolled in a Performance Improvement Plan (PIP) at Amazon, it is really important to know about the process and what are you expecting from it. Typically, the PIP lasts from 30 to 60 days and serves as a performance improvement tool based on employee-specific goals established by management.
During this time, your friend should work on meeting those objectives and get regular feedback. Record any progress made, and throughout the process, communicate with management. If this has a material impact on performance, they may succeed in getting out of the plans; if not, termination would likely follow.
Cheer your friend to keep them motivated and active. For example, they may want to ask for help from their colleagues or mentors and look into different ways to develop strengths.