You need to discipline her. I think spanking is okay, but since she's only 3 be gentle. It will definitely hurt doing this to your child, but I think it's more damaging to your daughter if you just let her behave this way. Send her to time out, take away her favorite snack or TV show. Think of it as training her. You want her to grow up into a good kid. Being too nice can result in your kid to thinking, "Hey, I can do whatever I want and my mom wouldn't do anything." They get worse and worse as they get older, so it's best to be strict now. There's a saying that you want to spoil your grandchildren, not your kids. It will be difficult trying to discipline her, but patience is key. Good luck.