Of course, there were theories about the victim's identity. She might have been a local prostitute, because every British murder investigation since Jack the Ripper is legally required to have at least one line of sex worker investigation. She might also have been a Dutch woman who had too much to drink, passed out, and was fatally shoved in a tree in a weird attempt to scare her into sobriety from a local dude called Jack Mossop and his Dutch cohort. Curiously, Mossop died in an insane asylum before the body was found. He had been committed there because of recurring nightmares about a woman staring at him from inside a tree.
But the real mystery of "Bella in the Wych Elm" happened after she was found, and in fact is the reason we know her as "Bella" at all. See, someone in the area knew, if not what had happened, at least who it had happened to. Soon after the body was found, mysterious graffiti with the words Who Put Bella in the Wych Elm? started appearing in the area, and variations of the phrase have continued to sporadically pop up to this very day.
Wait, hold the s**t on. Mysterious haunting phrase that keeps turning up no matter what. "Wych elm" (which is just a type of tree, but hey, witch allusions). Mental asylums. Haunting dreams.
God dammit, this is a vengeful ghosts thing, isn't it?