"Good job team! One clue to go and only 7/12 doom. We did it handsome today. All right, now let's see about this forced ability on Annette... Discard three cards and --gulp--, well that's two witches we didn't need right now. So we add two doom for them, one for Annette, one for the mythos phase. Holy smokes, 11/12! We're barely gonna win this thing... And there's ancient evils. More like Circle Unfun..."
There's a simple way to keep Annette's insane doom acceleration from spoiling your evening. Have someone drag her off the Witches Circle. She'll spawn her sisters at her new location, giving you a chance to kill them before they can get to the witches circle and end your scenario. Or, if you have sufficient health, just let Annette and her coven smack you around for a couple turns while your colleagues clean up the clues. As long as the witches are engaged, they won't move to the Witches Crcle, as per the instruction on Agenda 2a.