Hey there - sorry for the delay on this (I had stepped away from WS to spend some time with the kids). Here's what I have (hope it's worth the wait, lol):
So, my DW has finally given me the green light to share this (I haven't up to this point because she asked me not to):
She actually went to school in Indiana with both BM and SM. She was closer to BM, but knew them both.
So here's something strange that she actually called into the tipline a few months ago: she was FB friends with BM, but not SM. A number of her classmates were also FB friends with BM and not SM. As they were discussing this after the disappearance, many of them noticed the same thing. On the weekend that SM went missing, many of them had her pop up on their FB feed as "People You May Know" or "Friend Suggestions". My DW remembered it because she almost sent SM a message to the effect of "you never age", but didn't. She said she doesn't remember SM ever popping up on her FB under either of those categories before.... but that weekend, she kept popping up time and time again (and her friends said the same thing). She couldn't remember the exact timing of the suggestions popping up, but it was definitely Mother's Day weekend. Anyway, with the information that has come out re: the suspicious social media activity after SM's interrupted conversation with her friend - I think this all fits, JMO, MOO. I did a little research on the PYMK algorithms for FB, and they seem to be a bit of a mystery - but those suggestions are definitely tied to some kind of activity.... at first I thought it might have meant SMs phone (or other electronic device that she was logged into FB) might be close-by in Indiana, but I think that's unlikely - there was probably something else going on that triggered these suggestions. Again, JMO, MOO.