I don't think Maura was pregnant; the drinking involved in both accidents and the trip to the liquor store makes that unlikely; she was a nursing student and would known the ramifications of drinking while pregnant. There is nothing in her history to indicate someone who would deliberately make such a bad choice. I do think she may have had something of a "drinking problem," that is, using drinking to relax or deal with stress and getting into "problems" over that.
I've never thought the situation(s) that made Maura want to get away (for a week? longer?) were the same as what led to her disappearance after the wreck.
Firat, we know she was calling for a place to stay and made no effort to cover her tracks. She was in touch with her boyfriend; she hadn't cut those ties, as far as we know, based on his statements. She was dealing with the first car wreck issues and the insurance. So I don't think she intended to disappear or commit suicide when she left school.
However, the second accident put her in a terrible position--the alcohol spilled in the car, another wrecked car, more mess and trouble. Clearly the wreck, the drinking, and whatever was bothering her in the first place led to some bad decisions--taking off to avoid the police, being out in the dark and the cold in a strange and isolated area. I could see her walking away if she took things that really mattered with her. She might have started out looking for help and then later
decided not to go back, I guess, once she thought about things. Or something very bad happened. What I guess I'm saying is that the accident moved things in some new direction, and what was a "time out" became something else. I don't think knowing what went on before would explain her disappearance, but it might explain why she was willing to avoid the police. I don't get why she wouldn't empty that soda bottle and dispose of it if she were worried about "getting caught."
I guess that is why tthis case is such a mystery--where was she going, after the accident? And why did her tracks stop? I think everything that happened put her on a collision course with someone who met her within minutes of the wreck and that was either fatal or the impetus to walk away fro. her old life.