I doubt it, especially since the only evidence I've seen offered is her quick exit from Crawford. (Which was actually last Tuesday.)
Though she does know Rockwell, and even has participated in at least one fundraiser event for and with him.
But given her cohorts at CodePink I'd say it's far more likely she plays for the other team:
Cindy Sheehan Resumes Her Stalking | Sweetness & Light
http://www.sweetness-light.com/archive/cindy-sheehan-fresh-from-lebanon-back-in-ditch
Scroll down to see Cindy's person assistant, Tiffany.
I don't understand your reference to Tiffany. Tiffany is one of her political operatives. Cindy teamed up with Code Pink in the anti-war movement relatively early on and Cindy's been with Medea at countless events. That's why Melanie was aghast that Capitol Police didn't recognize Medea when she entered the Capitol for Maliki's speech. Medea's been pulled out of Bush events before in the past to boot!