I'm a college student living in a small city in the US. I am currently sharing an apartment with two other women (Jane and Mary), both in their early 20s. We each have our own bedroom but share a kitchen and living room. We didn't know each other prior to living together but have become friendly. We are pretty good at communicating with one another and speak to each other daily. However, Jane and I have been having problems with Mary for the past few months. There is no way we can move out or force her to move out; we must stay on the lease for the rest of the year.
Mary is loud and disrespectful (but not mean or aggressive). She frequently does things that either inconvenience Jane and I or put our health and safety at risk. Usually, she gives the justification that she was running late somewhere, drunk, or just scatterbrained when confronted.
For context, some of the things Mary has done that upset us include smoking in the apartment, forgetting to lock the front door, having guys over (this past week, 5 nights) and making noise until 2-3am, and leaving dishes in the sink for several days. Most recently, she left on a trip without telling us, leaving me to care for her cat. She often has people over with no notice, takes up the entire shared living area, and plays music or talks loudly.
Jane and I have tried several methods to improve Mary's behavior as a roommate (using advice from other, similar, roommate-conflict questions on IPS like: this one and this one,). We've tried to model good behavior. We have made a few rules, such as no smoking and no loud noise past midnight on weekdays, that everyone has agreed to. We talk to Mary within a day or two of individual issues occurring. I try to be empathetic; I know life can be hard for young adults and I often offer to help Mary with cleaning.
An example of what a confrontation usually looks like is (borrowed from this answer):
Hey, Mary. I'm pretty tired for my classes today; I got woken up late last night by voices. Could you try to keep it down? Maybe we could have quiet hours after midnight on weekdays, because it's hard for me to do my coursework when I can't sleep.
Mary always agrees to change her behavior, but it's been getting worse. A few days ago, we had a meeting, where we discussed Mary's noise causing chronic sleep deprivation for Jane. Mary was dismissive. Tonight, it's back to the same behavior. I have escalated my language, for instance the door was left unlocked for the third time in two days and I told Mary that it was unacceptable that she was putting our safety at risk. She again brushed it off and has gone right back to leaving the door unlocked.
My question is, how can I get my roommate to understand that her actions are disrespectful and consequently act more respectfully when I have already tried speaking with her and setting boundaries? My goal is for my respectful behavior to be reciprocated; I'd like to remain friendly with Mary but it is not a requirement.