As a Wizard you have enough dispels and nullifies to really give a FM conniptions trying to MC or Charm your big creatures.
Remember that the FM is really action-starved. If she has to both remove Nullify AND cast a charm, she's not attacking that round. (Unless she used a Thoughtspore to remove nullify - in which case, why hasn't your Lord of Fire killed the Thoughtspore yet?)
Whenever you are ready to beat down the FM, just Dispel her force field. Wizard has enough mana generation that you can afford the 12 mana cost. And don't cast bear strength on your lord of fire, cast Falcon Precision so he can pierce through her defense.
With 32 base health, the FM is really squishy if you can get around her Defense and her Forcefield.