I'm very much NOT a techie person but I'm presuming LE can tell (if Mollie's computer is a laptop/portable), where she was using it? Although of course she wouldn't necessarily need to be online to be doing essays, whatever. Again presumably the computer was found in the house she was staying in, not anywhere else? So again this would suggest she made it back to the house.
I don't think the idea that she went out again to run is likely. I don't know the exact stats but I would think the odds of a stranger abduction once you are home drop dramatically as opposed to when you are in "transitional spaces". And when there doesn't seem to be any indicators of someone breaking in.
I do think the elephant in the room from the beginning has been, how and with who did she get to work with, if she didn't have the shared car? I would think LE would have asked family/friends/co-workers this straight away, and then nothing is said about it? Probably significant, they must know by now if she was in contact with anyone else that night to arrange a lift. Or if she wasn't, why wasn't she, what was the default arrangement? And if there is such a person, what are they saying about what happened in the morning or perhaps when they were in contact with Mollie the evening before? And does it add up, or not?