You do know there's an off button on mobile phones, don't you? If you don't want to be bothered, you can just switch if off.
That's not the point. If she had the cellphone on airplane mode, it would only be a matter of time before she turns it off to look something up. And no it's not as easy as saying she doesn't have any will power. She also doesn't want to be bothered ever, so no point in having a phone on airplane mode.
I'm not talking cellphone on airplane mode but turn off you phone and if that ways not working well you can live on some place not on range your eyes.