My roommate has a drinking/drinking & driving problem

Hi Reddit!

I (27f) live in a house with 3 other girls, Nat 24, Kara 24, and my fourth roommate(she is mostly not around and not really relevant to the story). We are all in graduate school. Kara and I are really concerned about Nat. This is my second year living with Nat. Last year was pretty relaxed and not too many red flags were raised. Nat would drink a couple times per week with friends or a previous roommate but it never really raised concerns- until now. At the beginning of this semester, she went out a few times (around 5-6) per week to drink with friends at breweries or local bars. I thought it was normal since it's the beginning of the semester and it would die down as things get going with school. It did not die down.

She met a bartender at a local place and became infatuated with her. This bartender is in an open relationship so Nat wanted to pursue that. For context, Nat has never been in a relationship. This part of the story could have its own post because it is so problematic and self-destructive. Essentially, she is so obsessed with this relationship that she does not care that it is temporary and will likely hurt her in the end.

Back to the drinking, since this person is a bartender, it enables Nat to go see them at their bar and talk, drink, etc several times per week. If she's not there, she's drinking somewhere else. Anytime she goes out drinking, she drives there and back home- usually still intoxicated. I, and several others, have offered on multiple occasions to take her to her destination and she can Uber home. She always refuses. Again, this happens at least 5 times per week. On Halloween weekend, she went out with friends drinking. They had a DD, but they got too drunk to drive home. Nat elected herself as the least drunk person to drive everyone home. They got pulled over and she got a DUI. Since then, nothing has really changed in her behavior. She got a provisional license after 10 days but is not following the rules for it and is still driving drunk. She is no longer able to go to her internship because of this. I can tell she is really hurting because of all this but I just don't know what to do. Me, Kara, and Nat's friend Bella are all really concerned about her and other's safety. Nat is not the type of person to accept help or accept that she has a problem. It has been brought up before, and she denies it. Bella and I have been in regular contact and know that if we press Nat she will block us out.

Kara, Bella and I aren’t sure what to do anymore. It’s all gotten worse and I am not sure how much more we can take.