kit may be right about getting out being the best ultimate solution. However, if she really wants to make sure the landlady doesn’t know where she moves to, she needs to make sure not to provide her old landlady as a reference to any potential new ones. Her current landlady might get a call some day that says “Hi, I’m Amy from Newplace Apartments. Is XXX a good tenant?” Whoops.
I have got to third the idea of talking to a woman’s center/shelter. They deal with this stuff all the time. They can help get the law involved, provide lawyers, and help get her set up in a new place. This situation is exactly what women’s centers are for.
Although I’m a lawyer, I’m not yours and not likely licensed in your jurisdiction. What follows is not legal advice, just practical advice that mirrors a lot of what you’ve already seen.
Tell her to go to the police. If the officer at the desk is not helpful, ask for the “watch commander,” who is the next person up the chain. If the watch commander is not helpful, ask for the captain, the lieutenant, the chief: basically, I think she will need to be persistent to get help from the police, only because you’re right that this doesn’t seem an “imminent danger” type of issue. As you go further up the chain, however, you get officers who are more likely to think big picture (including considering public relations), and so may get a better response. Also, as in all professions, there are some doozies working there, and unfortunately the first person she meets may not be good at his/her job. By going up the chain, you increase your odds of getting a response.
Second, if you post your jurisdiction, I’ll point you toward some low-cost or free legal resources. Most local bar associations have attorneys who staff free help lines or things like that. She can talk to one of them and see if she has other options under state law.
Frankly, I’m surprised the owner isn’t taking this more seriously. I’d argue that the BF is a de facto employee of the owner and so anything he does I’d argue the owner is liable for. I might win, I might lose, but the owner’s going to be in a bad spot if there are documented complaints about this guy and he actually does something.
Good luck.