If Renner's information about the credit card number theft is correct, I think the information may indicate a good answer to the question of why Maura was packed up, why she went north instead of going to class, and why she had certain items in her car. Maura may have decided to leave school, either because she was embarrassed or because nursing was a door that might be closed to her. Either way, she was done with that school. So she has to figure out what to do next. I propose that she decided to quit school and get a job in the mountains. She had just wrecked her dad's car and didn't want to get into something that would further upset him, so she decided to go north, look for a job as a waitress, etc., and maybe a place to live. (The attempted trip to his motel room might have been intended to tell her father about her situation but the wreck made talking about theft and arrest and a record much harder to do.) If she went north and got a job, she could present her decision as a fait accompli. She got her room packed up and ready to go, and put stuff important to her in the car. She might have put the books in the car to sell later (no need to pack them) or to study if her job search came to nothing.
This scenario would even explain why we (the public) haven't heard about someone in NH or Vt that she planned to meet as well as why she had the stuff she had with her. She might have hoped to run into aquaintances up there but the trip was about starting over.
Then the second accident happens and she CAN'T be found at another accident scene with alcohol in the car (since the spilled liquid is going to raise questions) or in her system (either way). So she has to walk out of there. In that moment, she had to have lots of concern about how another incident would impact the credit card situation.
None of that tells us what happened once she decided to leave the car. If she ran, in unfamiliar territory and snowy roads in the dark, she might be able to do 7-8 minute miles: walking, probably 10-15 minute miles. So in 15 minutes, she might have 1-2 miles up the road. The question is--how far would she have to go to get to a public place for warmth, food, shelter? Is there a turn that might have taken the possibility of shelter out of the equation and made her more vulnerable to hypothermia or exposure? And of course, did she roll the dice and risk taking a ride? If Renner's information is correct, it resolves, I think, a lot of the mystery of Maura's trip. And we can focus on where she went once she left the car.