You are correct in your idea that you cannot instantiate an interface directly. But this is not relevant to Throwable, as it's a class.
Note that you should never instantiate Throwable directly, in any real application. It is legal Java to do so, but very bad practice. You should only instantiate Exception, RuntimeException or Error, or (better) their subclasses.
Betty Rubble? Well, I would go with Betty... but I'd be thinking of Wilma.