With that in mind, your mother-in-law is incorrect if she thinks that it is wrong to take away trick-or-treating from your kid. Why in the world would you take your daughter out trick-or-treating when she has shown that she could, at any time, have an embarrassing temper tantrum? She’s not ready to be in public with you yet. Not letting her outside with you until she can show you that she can be tantrum-free, is a good, logical consequence. 4.5 points for Mom.
On the other hand, not allowing her to participate in a school Halloween party or ingest candy in the fall are not logical consequences. You are arbitrarily taking something away because she was obnoxious at the store. This will only serve to create a power struggle. She won’t learn anything from it. Logical consequences involve learning (in this case, learning that she can be in public with mommy as long as mommy knows that she will be pleasant). Punishment just involves randomly assigned pain (in this case, taking away parties and candy). Your mother-in-law is right that you didn’t handle this perfectly, but I don’t think she is even aware why or how she is right, so I am only awarding her a single point.
After removing your daughter from the store, just like you did, I would have let her know that I was going to do something about this. Sometime during the day on Beggar’s Night, I would have the following conversation:
Kid Whisperer: Oh, boy. Remember when you had that tantrum at the grocery store and we had to leave last week?
Kid: How could I forget? Let me guess: you have come to your senses and are about to present me with a doll and an apology.
Kid Whisperer: Nope. I am worried that, based on your actions at the grocery store, you may throw another embarrassing tantrum, and I’m not willing to risk that. Your sister is going out with your father to get candy, and you will stay here with me to practice not throwing a tantrum and being nice. This will be the case after school and on the weekends until I can trust that you won’t throw tantrums and will be pleasant.
Kid: NO! NO! NO! I’ll be good! I promise!
Kid Whisperer: That’s good to hear. I know that you will show me that you won’t have tantrums anymore and I’m looking forward to seeing you not have tantrums at home tonight.
Tell your mother-in-law that she has had her chance to raise kids, and thank her for raising your fantastic husband. Let her know that it is now your turn, you will take it from here, that you won by 3.5 points, and that the score is final.