How to deal with subtle harassment and retaliation at work?

My girlfriend recently approached some loud and rambunctious coworkers in the office next to hers to asked them to quiet down so she could work. Since then, they’ve made it a point to pass by her office and be louder than ever before. They shout over each other, then peek their heads into her office and “shhhh” loudly at each other, and keep repeating “be quiet” over and over again within her hearing. They point at her and laugh, gesticulate and generally act very rudely (need I mention these guys are probably twice her age?).

She’s tried complaining to her own supervisor and the supervisor of her rude coworkers, but she’s been given the runaround while the retaliation continues.

Her nerves are worn thin and she doesn’t even want to go into work anymore. What to do in this situation?

I suggested to her that I should go in and talk to them, but she vetoed the idea. She called HR, but they said it would have to wait until Monday. Now she wants to call the CEO directly. I also suggested telling both supervisors that she would be complaining to a government agency if action isn’t taken (though I don’t know which government agency is responsible for this kind of thing).

Is there any way to resolve this situation?