One thing that every employee needs to understand is that HR is not your friend. No matter how friendly or helpful they seem, their job is not to protect you. It's to protect the company.
Sure, but what's the alternative, especially in a case like this? Your manager is engaging in harassment, HR is where you "should" raise this. Her following protocol also makes her case stronger I would argue. You gave your company the chance to make things right. After that I'd say the gloves could come off if that's the route you want to go.
Contact your state's labour commissioner. If you received stock or stock options, contact your state securities commissioner. Otherwise, suing is tried and true.