It's happening. My eldest is six. And I've noticed that when it comes to being a stubborn git, she's definitely more her Mum than she is me.
She'll refuse to do the most benign things. Getting dressed and brushing her teeth is an absolute battle. Trying to get her to eat anything that's not a ketchup covered fish finger? An Impossibility. She's her Mum. Classic 'cutting off her nose to spite her face' sort of stuff.
Ay ay ay.