It's not uncommon for drunks/addicts to go on one last binge before entering rehab. She was probably nervous as hell about the program and alcoholics turn to alcohol when they are emotionally distraught about anything. Her history of depression just made the situation worse.
I totally believe the suicide angle is the most likely possibility. Here she is, about to enter rehab, and is arrested by airport cops because she got on a binge on the way there and assaulted other people. She was mortified (in the classic sense of the word) by what people would think and couldn't face it.
I work in Emergency Medicine, and about 80% of the people who show up in the ER to “get admitted for rehab” do it totally drunk or stoned. A significant number leave within 24 hours. You would not believe the millions upon millions of wasted healthcare dollars running these people through the mill over and over and over. I’ve seen people who have been “detoxed” in the hospital 3 or 4 time in a month.
Kaiser in California had the best answer. They only did outpatient rehab ( studies show NO long term diffence in outcomes, you don’t live in the hospital after all). If you showed up in the ER we took care of any medical issues, gave you a script for a couple of Librium to take the edge off, and gave them a referral to outpatient Rehab the next day, where they were told to show up SOBER and with a ride. If they were serious about getting straight they did, if they weren’t , too bad.