What's a mother to do??

For the most part Emma is doing well adjusting to going to school 5 days a week. We have had a few little problems...but not too bad. There was the sticking the tongue out at her friend day (2x) and the I won't get out of the car without my purse stuffed with toys day. But nothing horrible. She had actually managed to go 9 whole days without having her name put on the "sad" side of the board......until today. So, I picked Emma up from school today and usually the first thing she says is " Mommy, Mommy I didn't get on the sad side today." But today????? Not a word. So, I say " Emma, how was school today?" She starts crying and says " please don't tell Daddy". So as it turns out, today at PE, there was a little problem. Apparently, this is the 4 year old version, Avery wanted to be in her "club" and Emma did not want her to be, so she told her no. Then Avery tells the teacher Emma won't let her be in her club. The teacher tells Avery not to tattle. So, Avery asks her again. Again, Emma says no...of course. Avery goes back to the teacher and tattles. The teacher then tells Avery she has to sit in time out for disobeying her. So, get this. While Avery is in time out, she is talking to the other children. Emma tells Avery that she is not supposed to be talking while she is in time out. Bossy little thing.....where does she get this from??? So, Avery continues to talk. So what do you think Emma did???? She told the teacher. So, then there Emma was....in time out....next to Avery...for doing the exact same thing. Helloooooo....were we not paying attention?? Does she think that the rules apply to everyone else and not her??? So, being the horrible Mother I am, I laugh. I am sorry, but I think that is pretty funny. She so deserved her punishment!!! Emma didn't think it was funny and didn't appreciate me laughing. Like they say my sweet Emma....what comes around, goes around. So, what's a Mother to do??? Laugh? Punish? I always pray that if Emma does something wrong, she will be found out right away and that the punishment it swift. I don't want her to ever think that she has gotten away with something, even if only briefly. I want her to always think " it just isn't worth it....".
So, what would you have done????