Gender Stereotyping - Opposite of mom?

Have you ever noticed that at Halloween most little girls are princesses and most boys dress as super heroes? My human growth and development textbook lists age 5 as the time when children tend to categorize themselves into male or female. In the social learning model they model their behavior after either their mom or their dad. So will someone please explain this to me???? My daughter Danica is tomboy, she played rugby in high school. As a mother she MIGHT put on makeup and a skirt for church, but it's sweatpants and jeans the rest of the week.

But her Lily. Oh my. Last Sunday Lily put on the sleeping beauty costume at my house and danced and lept around the room as Danica and I sang "I know you, I know what you'll do, you'll love me at once". Then she put on the Ariel costume and flipped her fish tail as we sang "Part of your world" then she thrust her little arms up into the air for the finale of the song. Where didthis feminine creature come from??????

Contrast that to this: Celeste is a little more of a girly mom, especially when it comes to acting and theatre. But her 5 year old daughter Brooklyn......well, she doesn't exactly fit the gender stereotype of princess. Brooklyn was invited to a sleeping beauty birthday party and was supposed to dress as either a princess or a knight. Brooklyn wanted to be a knight with a sword and "because knights rescue people". When the father of the birthday girl jumped out at a dragon, the little princesses ran away. Not Brooklyn. She and the boys fought the dragon with their swords. After a few minutes the boys lost interest, but not Brooklyn. she fought for another half hour. She asked for a pirate coat for her birthday. (sigh) I just don't get this.