What would you call?

[MNBlue]

NCAA Rule 9-8-b
"The batter shall not hinder the catcher or any other fielder from catching or throwing the ball by stepping out of the batter's box or intentionally hinder a player (e.g., on a steal/pickoff throw or a play at the plate) while standing within the batter's box."

note 2
"If the catcher or her throw to a base hits the batter or her bat while she is in the batter's box, the ball is live and there is no interference unless the contact is intentional and initiated by the batter."

Since in your scenario, the batter has left the batter's box, she has given up her protection the batter's box affords her. Now she is required to stay out of the way. Since she didn't, I would have interference, batter out, and return the runner to 3B.