[Fortunately the steps are smooth, so it won't be too rough her. And the steps are uneven and steep in some places, so it's probably better she was barefoot.]

The magic in this tree has it so even if you see the door, anyone not a guardian will ignore it. That's because...

[When they reach a landing, with more stairs still continuing up, there is a small, shuttered window that he opens for her to see out.]

This is like a sentry tower to help keep watch.