So she ditched the shoes she was wearing in the hallway at the doorway to your own room?

This is quite common, and often you'll see the maids wearing slippers. The underlying motive is that the room is your 'home' and it would be entirely natural and expected for a Japanese person to remove their shoes when entering another person's home.

Consider how rude it would be for hotel staff to walk into a room in their shoes when the hotel guests have taken pains not to.

Once you've adapted to the mindset of shoes off at the front door you start to see the habit of wearing outdoor shoes inside as being a bit disgusting. I don't even like to trundle a roller case over a room I'm staying in for similar reasons.