If she isn't filling the doorway you have a way out.
Nonsense. A linebacker doesn't fill a football field. How do they ever make a tackle? The fact is, you only have a way out if she chooses not to move and the both of you combined are less than 30". I doubt that this option is realistic in the event that she is angry with you.
Clearly running is not an option in every single scenario. There are times when an individual will have to accept a physical altercation however brief. In this scenario, one could remain in the bathroom and be assaulted or try to force their way out of the bathroom. This would require, at the very minimum, pushing.