in all honesty, dita is just plain good, but colettte has ways of dealing with her crew, low wound low df (for their ss cost) minions are exactly what colette will want to fight, with SS use she can reliably do 5wounds with a spell and when you factor a coryphee duet kiting around taking 2-4 wounds per hit off things it spells trouble for the guild player, sonnia however is a different matter, that counterspell makes hurting her very difficult, and while you can mke her pitch cards till the spell goes through (as Odin rightly said colette is very much about resource management, yours and your enemies) that means than she is dictating what spells work and more importantly when, which make sdoing any meaningful damage to her very difficult for colette (and barring marcus arcanists in general, oh and avatar ramos... god i hate that guy) and the coryphee wont go near her coourtosey of didasemble.
also witchling stalkers straig up shut down colette's damage output, the 3 big damage spells in the crew all have 2/3/5 damage arcs, which means the ability to cheat is quite important, which is difficult when your casting flips are on even with soulstones
definitely second odin on the point of: under no circumstances take hoffman! it is far too easy to stick his taxi in a bag, drop it at the other end of the board at the end of the turn and watch hoffman limp back towards the fight, also discharge soulstone + mask trigger = free 2/3/5 ignore armour spells targeting df (not the strong point of hoffmans constructs)
the disapearing act shennannigans are equaly valid on guardians (for this I tend to use doves).
playing competetive games against colette with guild I have found success with sonia and justice (advance as a blob and take the crew to pieces piece by piece, using justice to deter the coryphee). playing using colette against guiild I have struggled mainly against sonia, allthough i did have one game I lost horribly to hoffman, a colette-hoffman vs sonia-hoffman brawl at the uk GT, sonia in a hoffman tank is amazing, as is nino.
oh and make the manaquinne your first target, it is an amazing utility piece