If you and your boss reviewed your evaluation and it was satisfactory, and you both signed it can her supervisor force her to redo it . She redid it and he still refused to sign it because it was also satisfactory. She did a third that she had to make unsatisfactory so tah he would sign it. Can a boss do that to someone?

That's so wrong. If the person had a good evaluation which was signed off and was provided a copy (which they should have), and they changed it to unsatisfactory, I would be going to the Human Resources Dept.