I agree with the poor optics of the situation, but let's also acknowledge that the reason you have to shut them off "when the door closes" is so they can walk around and do their safety checks and tell you to turn off any devices you may be using. They sometimes do allow you to use them again if there will be a long tarmac delay but then would redo the check.

Now if she had continued to use the e-reader on takeoff that would have been a different story.