One of the ways of thinking a player needs to overcome to successfully fight a Forcemaster is that she fights fair. She doesn't fight fair.
She's fundamentally at an action disadvantage. No spawnpoints and very few creatures in her repertoir. She can't afford to fight fair. You have to expect your stuff to be out of position all of the time. No matter how many teleports and force pushes you bring you will never out position a Forcemaster.
The Forcemaster, to greater extent than the Druid and the Necromancer (depending on your book), is a mage that you have to actively make a plan against while building your book. The two most important things to overcome vs a Forcemaster are her positional advantage and her superior defenses.
Positional Advantage
1) Force Pull. A good Forcemaster will use this to isolate and destroy your army. This is baseline, no spellbook points. You have not learned how to play Forcemaster if you never use this ability in your games. Additional tools in this category include Force Push and Chant of Rage.
2) Mind's Eye. This spell is a trap. Attacking it is the worst thing you can do (imo). The best way to beat Mind's Eye is to close. Run up to the Forcemaster so that the action was wasted. Make the Eye a trap for her. If you turtle against Mind's Eye you lose. Granted, it's dangerous to run up to a Forcemaster, but you have to be within range to affect her and her stuff or you just lose to Mind's Eye.
Superior Defenses
1) Deflect. Deflect is her baseline 7+ defense. Tied for best defense in the game with Reflex Boots and Cobra Reflexes (9 mana each). The only way to reliably hit her is to Incapacitate her or use an Unavoidable attack. Knockdown and Surging Wave are tried and true tools here. Additional in school defenses are Dancing Scimitar, Force Orb/Sword, Block, Reverse Attack and the rising popular Symbiotic Orb.
2) Forcefield. If you don't have a plan vs Forcefield you lose. It completely cancels an entire attack every turn. Forcefield begins with 3 counters on it, so initially you have to knock off 3 counters in one round or 2 counters a round for 2 rounds to make any headway. The obvious choice is Dispel, but that will cost you 12 mana. Other options include Wall of Thorns + Force Push (which will still cost you 11 mana) or a horde of creatures all of which had better be able to survive a single 7 dice attack. Additional defenses in this category are Repulsion Field and Force Shield.
Fitting in either category are the control spells. Mind Seize, Mind Control, Charm, Song of Love, Lullaby. Each of them can turn into action, position or defensive advantages when played properly. One strategy vs the Forcemaster is to play Psychic Immune and Unmovable creatures. The issue with that is that you had better be able to overcome their (usual) Slow trait or you'll just get yanked away from them and diced yourself.
Since you asked about the Paladin, I actually think that Holy mages have a decent amount of options vs the Forcemaster. Blind, any healing, Aegis, Eye for an Eye, Divine Reversal, Restore and a host of Ethereal attacks (vs Mind's Eye or Stalker) and easy access to Healing Wand, Galvanize and Cure. Obviously, vs a Sleep Spore the Priestess is the most superior, but that doesn't change the other options you have.
As a final aside, the Siren is very similar. Many tactics that work against the Siren will work against the Forcemaster.
