Once again, everyone she was known to know has been accounted for. You're making up someone, who there is no proof existed and saying it's a more likely scenario than getting picked up by someone she didn't know. And saying her family should go that route. Smart.
As for walking off and dying, there was snow on the ground and no footprints leading from the scene. Maybe an alien ship snatched her up, that's just as likely as your original post.
You really are taking this too personally. We are all just throwing theories around at this point. There are three main theories. She died on her own. She was killed by some who knew her. She was killed by a local person. There is absolutely no evidence to support any of them. It pretty much just comes down to people's ideas and what they think is likely.
I lived in the dorms just like Maura did and people will have a lot of casual acquaintances that few people will know about. Chances are slim to none that we know about all the acquaintances Maura had living as a college student on campus.