What happened to my 10 wk old angel?

Yesterday, she was a perfect puppy - snuggly, listened, easy to entertain. Today she woke up and chose violence. I’ll tell her to sit and she just barks at me defiantly. She won’t listen to any commands and just cocks her heads, stares and barks. She will find something in the yard and play keep-away.

She just turned 10 weeks old. Is this the toddler phase?? She’s my first dog/puppy. Any and all advice is appreciated