I think you're very likely on to something, B. There's been a string of these "incidents," all somehow unsolved. I wonder if the police kept evidence from those? It would make sense that a serial hoaxer might be emboldened and sloppy enough to let herself be seen by wintesses, after getting away with other hoaxes.
Those two witnesses have a lot of courage to come forward. If this thing gets to trial, Dunn's lawyers will do everything possible to put the witnesses on trial, impugning their credibility and character. They are probably already doing intensive background research on them.
She's the only person with any motive. Hate crimes further her personal agenda and would have empowered her if she wasn't found to be the perpetrator.