It is actually about 4 miles from the high school to Cranmore Mountain Resort. It's 2 miles from the high school to where Abby lives. If she was walking (and texting) the average speed for a woman of 3 miles per hour, and she was always walking in the direction of her home, then in 37 minutes the furthest she probably would have gotten was 2 miles (or around the area of her home). Since there's no evidence - according to LE - that she made it home, and her last text was at 2:53, or about 23 minutes after she left the high school, she may have walked about a mile before her last text.
Unless she was running/jogging the whole way, it seems unlikely that she could have gotten to Cranmore or due west of there by 3:07, so at some point it seems she and/or her phone got a ride at least that far.