Miss Violet has been learning her body parts. All of them. Yes, she's aware that she and her brother are not the same. She completely understands that girls have a 'gina and boys have a peeeeenus.
Here's a conversation with her father that I overheard:
Scott: Does Milo have a penis?
Violet: Yes. He's a boy.
Scott: Do you have a penis?
Violet: No. I'm a girl. I have a 'gina.
Scott: What about Mocha? (One of our dogs)
Violet: She has a tail, daddy. She's a dog!
Yep... That's my funny girl...