Think of the sun reflecting off someone's car rear window into your eye while you're driving. I suspect it felt much the same to her in the darkened cabin.

If your overhead light reflected off the screen of your Kindle directly into my eye, I would also ask you politely to either move the device so it didn't do that, or turn off the light. Was she rude to you? If not, I don't see how her request was unreasonable.