I think sis's friend works for the "3rd" side, she knows about neverwhere, left sis alone in a bar, 3 idiots try to kidnap a drunk sis, say "She should have been alone."
That's how they threw us a bone for research)
We dig deeper, if her friend is there, the very Jai that Nightingale is looking for, and she arranged all this because of the death of her parents, so that the Templars and the elves would kill each other. She may even be able to telepathically inspire thoughts or control a person. Otherwise, why would Jess have such a lapse in memory, skipping days and she easily agreed to go to the neverwhere club? Where she was suddenly left alone without even being embarrassed, like how obvious it could still be.
And Sayo will also say, in the next update, that suddenly her memory didn't remember anything, and she was being manipulated like a puppet.