Is it possible now with technology to locate the phone? would she have had the "find my phone" app or something , sorry not tech savvy. Also there are a lot of cameras along that route surely they can pinpoint when last seen and if she made it home? Did she live alone or with boyfriend , its not clear? Either she was abducted or attacked, if attacked then in 5 days i would have thought they would have found her? How was she when she left her friends? did she usually walk alone?
I hoping for a happy ending to this , but it does seem unlikely.