Her VSCO and Instagram and FB (IIRC) were all open to the public. There was no need for someone to come and stalk her in person to gain, very personal info that could have led to her abduction. All they had to do was comb through her social media to learn her routines. From her Twitter alone, without even logging in, you are able to learn:
- Full Name
- School
- Class schedule
- Her mom's exact address
- The full names of several friends
- The fact that her boyfriend leaves for long periods of time
- Her political views
- The fact that she's a runner
- and more...
She could have been being stalked, remotely, for quite a while without ever even being aware of it. SM can be like an "All Access Pass" to a persons life, habits, friends, family, hobbies, hangouts, personal weaknesses ect...
(If anything, this case should be a teaching moment to set your SM to friends and only add those whom you trust.)