There would have been footprints in the snow. This makes me believe she stayed on the road. The question is for how long?
I agree, she likely left the accident scene on the roadway for some period of time, how long is impossible to know of course.
I do think this possibility is fairly consistent with what we know of her state of mind immediately after the accident. She refused help from Butch, and she lied to him about calling AAA.
We know that she made some effort to leave the accident scene as quickly as possible based on the time short between when 911 was called and when the first officer arrived on scene. It stands to reason that her intent as that time was to avoid contact with police and to leave the scene as soon as possible.
We also know or believe that she took most of the alcohol she bought, Vodka, Baileys, and Kahlua, other than the box of wine, and she took her backback and some of the sleeping pills as well.
Based on that alone it seems reasonable to conclude that she would have left on the roadway, at a run or perhaps fast walk, and she may have taken steps to avoid being seen by any car traffic she could see on the road, which would have been possible considering it was dark and and she could see any headlights approaching with enough time to avoid being seen.
So how far did she go? An athlete with some level of adrenaline could fairly get a mile or so from the scene in about 8-10 minutes even if she was walking fast or jogging. By the time the police arrived on scene she could have been 2 miles from the scene and outside of the search area. Given another 20-30 minutes she could easily have been 4 -5 miles away, far enough that no searches conducted would have even come close to where she could have gone into to woods.
Obviously she could also have gotten a ride once she got a mile down the road, putting her well outside of any search area.
It is also worth noting that the location where the dog track ended is in fact right in front of where Butch parked his bus. So the theory that she walked to that location and then got in a car seems unlikely as either Butch or his wife would likely have seen a car stopping in front of the house.
In my experience people who are in a stressful situation such as after a car accident, and may have been drinking, are able to walk or run quite a distance from the scene just on adrenaline alone. It is also not uncommon for people to walk up to 10 miles to get away from a potential DWI, late at night in the cold and even highly intoxicated.
If she wanted to get away from that car and avoid any police she could easily have done so and been far outside of the search area. That leaves a vast and very desolate area accessible to her to disappear and never be found.
One item in particular that she brought with her is very telling of her possible intentions, in my opinion anyway. That book she brought was titled, "Not Without Peril". Many people have suggested this may be a guide or resource to hiking in the White Mountains, it is not that at all. It is actually a very tragic book comprised of many stories of death by climbers and hikers in the White Mountains, specifically Mount Washington. If a person were considering or contemplating suicide by hiking into the unknown this would be a book they might bring. It is a really great book well worth reading.