I work at a university & have some experience dealing with situations you are describing.
From what you have said about this girl’s behaviour, there is no way that she is not already on the university’s radar.
Even if she has dropped out, she will still be a registered student until at least the end of the academic year, when she would be formally withdrawn during the Exam Boards & therefore, they have a duty of care here, both to her & the other girls.
So, you & your daughter should get on to student services & the accommodation office. Only one student need attend a meeting, but email them in advance with ALL the details, all the verbal abuse, the locking out, the threats & sign it from all the girls in the house, with them in cc, making sure you use their university email addresses. All parents in cc as well.
You should also include the student discipline office in this email.
Student discipline is not just about behaviour at uni, but outside as well, if it is damaging to other students & damages the reputation of the university.
Make sure you say that this girls behaviour is frightening, is harming your daughters ability to study/participate fully on their placement & is having an effect on her/their mental health.
As others have said, someone needs to be ringing the letting agent every day & get them to step in.
Good luck.