Not quite, IMO - Edit 1
Before modification by BlackAdder at 13/01/2010 11:54:55 PM
Sorilea didn't act like a darkfriend around Semirhage. She was insulted by Semirhage comments, and suggested to Cadsuane that they should kill her rather than imprison her. Yeah, maybe it's all a big act - but then, maybe Nynaeve is acting too.
It's obvious that Ishamael and the Shadow have given up on Semi (except to Semi herself).
The DFs we've seen are all very selfish. Even Alviarin is scheming to usurp Mesaana, surely. It's the only way you move up in Shadow society, but pulling down your superiors.
Sorilea thus has motive to pull down Semi and has immunity from any retribution from other Forsaken because Semi was ordered not to be helped anyway.