Good day

I received this question from a friend and I thought I would post it here to see if I can assist her with some advice.
The situation she described to me sounds like her current-Line manager is throwing Mud to see if something sticks.
Where all her previous line-managers (all 4 of them) in the same company gave her one performance bonus or performance increase after the other,
The latest line manager (after the most recent management change in the company) decided to hold a performance review and make allegations of poor performance.
She dismissed every allegation with proof, in her reply on the formal enquiry document.
Now she wants to know if she has grounds to lodge a grievance against the line manager, directly with the HR executive?
She told me that she does not feel like she can trust her line manager now, after she washed off the mud