Oh the curiosity! Izzie just came up to me and said, "I'm not tattling right now. Maddie did something bad, but I am not telling you so I won't tattle."
I told her that maybe she should go tell her sister that she thinks she's making a bad choice and that maybe Maddie should go talk to me about it. So off Izzie went to talk to Maddie. I also told her that if Maddie was doing something dangerous that she could tell me and it wouldn't be tattling.
I'll go talk to Maddie in a bit, but I figured I'd give her some time to come to me first.
Later: Maddie did come to talk to me, it really wasn't a big deal... she put a toy in her mouth, which of course is against the rules. So this was more about Izzie trying to learn when it is okay to tattle than anything Maddie did.