
Bree is Harry and Op is She Who Must Not Be Named. Jonas and DB are Ron and Hermione respectively and, as I see it, they are toast. Something bad has to happen to them (worse than we've seen already) to get Bree fighting mad enough to take on Oppy. Either they will betray her somehow (perhaps unintentionally) or they will be harmed in some way.
Or, to look at it another way, Jonas is tin man and DB is scarecrow. Somebody is going to have to set DB on fire or rust the hell out of Jonas to get Bree mad enough to pick up that bucket of water and destroy the evil for good. Nobody can do it for her. She has to find that power within herself. Tachy is Glenda the good and Brother, rather a bumbler, is the Wizard.