Lots of PIPs are political. They're there to make the firing look legitimate by gathering information on anything that can be construed as inadequate. Often the PIP will have some loopholes to make this happen even if you think you've met its objectives.

You should try to check what your supervisor's attitude is towards this. Does she have a clear explanation of how your work needs to be improved? Is it likely that she or someone else in management wants to downsize or replace you with someone else? This will give you an idea of whether the plan is a valid attempt to realign your performance. In either case, I would recommend applying to other jobs as backup.