A year or two ago, a documentary was made on Tammy. This past season, she appeared on the television show The Surreal Life.
I missed the film. But between what clips I saw of that, and the Surreal Life episodes I caught, my impression is that Tammy is Maude Flanders. She was naive, enthusiastic, and got carried away when the money started rolling in. She bought an air conditioned dog house and other luxuries because it seemed like a good idea at the time.
From everything I’ve seen of Tammy, her faith is actually genuine. IMHO Tammy wasn’t Jim’s accomplice in fleecing the flock. She was another victim he’d deceived.