I actually think there is quite a lot of evidence that suggests she didnt intend to disappear and then met with foul play its a bit complicated to unravel, but it is there.
Something that suggests to me she wasnt planning to start a new life is that she checked her cellphone messages before she set off on her journey. Heck, the fact she took the phone with her at all indicates she intended to continue taking and making calls. If she didnt want to ever see any of the people in her life again, why would it matter if they left her a message? Why not just chuck the phone, or leave it behind?
Then, there is her bank. She was due to be paid for her Uni job in a few days. Wouldnt it have made sense for her to wait until that cleared before she set off, if she really wanted a new life?
Then, why did she pack her stuff into boxes? She would have had the sense to realise her stuff would be investigated if she just disappeared. To me, that suggests she intended to come get the stuff and leave the Uni quickly and quietly at a later date.
Why did she search for directions to places she had visited before? Why phone the GoStowe line? Thats not really far enough or removed enough for starting a new life. Why not directions for Canada, or Mexico, or to an airport?
I just think she had to get out of town for some reason. I still have a suspicion that she was heading towards a local-ish town to stay a night or two and actually sort something out be it a medical problem she had, organising a visit to a University, some way to claw herself out of the problems she found herself in. She was taking a proactive and essential step forwards, not running away from a life she couldnt handle.
Gods, I wish it had been possible to phone every hotel, hostel or bed/breakfast in NH to find out if anyone missed a reservation in those early days of the investigation.