My issue with a lot of the advice given is it's temporary - the FM backs off, uses her innate push ability a bit and the FF is back up to 3 charges quick as anything.
Dispel is, clearly, the best choice, but a Nullify on her when you cast it could literally make you cry... This means you've gotta cast something else on her first to make sure you get it through, and THEN the 12 point Dispel... For those unfortunate mages that have a channeling of 9, thats a LOT of mana.
What you have to do is COMPLETELY alter your strategy to try desperately to remove one card of your opponents. While they try to savage you about the head and neck... That's an extremely powerful card.