A classic pseuicide
With thanks to @doctoraicha on Twitter--
I'm just going to link to what is already a very thorough writeup, but let's just say that when I got to
she talked a lot about her boyfriend, Jeff, and her best friend, Lexie, and both of them actually had occasionally-used FF accounts and would sometimes participate in AIM chats with the rest of us
I knew exactly where this was going, and I think you will too. (With a bonus Facebook twist!) Commenter irishmizzy dubs it "CATFISH 2: EXPECTO PATRONUM," which is about the way of it.