My sister (f/20) is a Music Education major at a state school in Illinois. In her Freshman year, she became very good friends with another girl (f/20) in the same program. They played similar instruments, had similar interests, pretty typical BFF behaviour. During their Freshman year, they lived with other people, but due to these other roommates making other arrangements, they decided to be suite mates their Sophomore year. They lived in a suite of two bedrooms with a common lounge room, shared by four people, with a public bathroom shared by the whole floor.

Shortly after the beginning of Sophomore Year (2018-2019), my sister's roommate, who shall henceforth be called 'Abuser', began engaging in some concerning behaviours. She became very possessive over Sister's time and attention, seemingly wanting Sister to make her whole life revolve around the Abuser. Much of this was accomplished by petty, passive-aggressive behaviours that on their own would be annoying, but not worth pursuing, such as moving Sister's things while she was not in the room, turning up the volume on the television when asked to keep it down, and hiding the remote for the TV (which is actually my sister's personal property).

These things are not exactly abusive, but just inconsiderate behaviours, so Sister was willing to write them off as being things that would gradually ease up over time. But things did not end there. Abuser's family does not have a lot of money, so it's understandable that they would try to cut corners in some placed, but numerous times in this period, Abuser guilted and manipulated my sister into believing that it was her responsibility as a friend to buy her things such as food, textbooks, and household products such as laundry detergent and feminine hygiene products. This behaviour escalated into an incident where, before a break, Abuser had been borrowing my sister's textbook to complete and assignment, and when asked to return it so that my sister could also complete the assignment (which was due after break), she outright refused. My mother, who actually paid for the item, had to step in to have it returned.

Perhaps the most outrageous and inappropriate behaviour is Abuser's numerous tactics to cause emotional distress and physically and psychologically isolate Sister from her friends. My sister is a very sweet girl who tends to give people the benefit of the doubt, our parents and I, being older and more cynical, had Abuser figured out much earlier, and discreetly encouraged Sister to not lay all of her friendship eggs in one basket. We stopped extending invitations for Abuser to stay with us over breaks or weekends, or to join us for dinner when we were visiting for campus events (music performances, family weekends, etc). All of this coincided with repeated criticism from Abuser in regards to how much my sister called us on the phone, video-chatted or texted us. Sister has always been very close with our mother, and usually calls her once a day. She also plays video games with me online from time-to-time. Abuser attempted to have Sister cease any communication with us, calling us 'bad people' and saying that we were against her, which... honestly, wasn't a lie by this point. This actually worked to some extent and my mother experienced severe anxiety in regards to Sister's lack of communication being an indicator of something bad.

Abuser would also ignore my sister for long periods of time (usually a week or two at a time) for insignificant things (such as Sister leaving her Netflix account logged in, on her own TV that she owned). I'm not talking that they just didn't hang out. Abuser straight up pretended like Sister did not exist, while cohabitating in a single room, and still helping herself to borrow sister's textbooks, television (Abuser actually also had her own television), and media streaming accounts (which were actually paid for by me - passwords have since been changed). She also, through passive-aggressive, and often point-blank bullying behaviour, has driven three people out of sharing their suite. One of these three has dropped out, citing psychological issues caused by Abuser, and another is still in school, but has started seeing a Psychologist, who has stated that Abuser is a major 'trigger' for her depression and anxiety.

At this point, Sister has decided to terminate the friendship altogether. She made different friends, joined different on-campus groups that have been very supportive, and even started a relationship. However, Abuser has pursued Sister to these groups, and tried to systematically manipulate them to isolate my sister. This has actually largely not worked, but is a source of constant psychological and emotional stress. When Sister's romantic relationship ended, Abuser even began inviting sister's ex to the suite in order to alienate Sister and prevent her from using common areas or feel comfortable in her space. This escalated to the point where several of Sister's friends thought she may be suicidal and took her to the hospital, where she was voluntarily held for a few hours and then released as she had not actually made any suicide threats.

Most recently, Sister was made the section leader of the flute section. Abuser is in this group and goes out of her way to constantly challenge Sister's authority, or deliberately ignore requests or instructions. Since they are also the same major, and class sizes are small, it is unavoidable that they share several courses together. Abuser has engaged in passive aggressive and sometimes outright intimidation to prevent Sister from attending classes, being able to focus and has generally disrupted her learning. They were actually supposed to work on a group project together, but Abuser outright refused to participate. The faculty has now been informed, but it is too late and Sister will have to retake a few of her courses next semester. It's not the end of the world since Sister transferred into Music Ed from Music Therapy and was going to have to do 9 semesters anyway in order to catch up.

Some of this behaviour has been reported to the University system, including University police. Unfortunately, they are not able to take action that is satisfactory. So I am left wondering a number of things:

a. Is there legal action we could take to either Criminal or Civil? My sister does not actually want to take any official legal action at this time, but wants to know what options are open to her. Is it worth paying a few hundred dollars to consult a lawyer?

b. Is it possible to request a restraining order against Abuser? Most of the resources I've found are specific to domestic abuse and stalking, neither of which are quite right for this case.

c. If we are able to take legal action or get a restraining order, would this mean that Sister would have to change residences/schools? Or would Abuser be obligated to make other arrangements as she is the one engaged in the bad behaviour? I believe it would be more damaging psychologically to have Sister obligated to change schools/residences than it would be to deal with this through the University. The University is just kicking their feet a little bit and floundering on taking decisive action.

TL;DR: Sister has a roommate who engages in mentally/emotionally/psychologically abusive behaviour. University is not taking appropriate action. Please help.

Thank you in advance for any suggestions or advice. I am obviously speaking a little bit on Sister's behalf (she does not use Reddit), and so I may not be able to provide immediate elaboration on certain details. The behaviours described above are not even all of the documented behaviours, just the highlights.

Edit: Sister does not actually live with Abuser anymore. However, since their required courses are similar, and their program is small, they are often in contact. Abuser specifically seeks her out to continue engaging in this behaviour.