If she is plucking she may be doing it on the nest as it's preparing the nest for babies. That could be why you haven't noticed.She appears to be her usual cheerful self, just feeling the heat around 3-6pm every day. That's when she drinks, sits in the shade, pants, and waits for the day to cool down. That's normal for Mary on a hot day. (Tomorrow will be super hot, so at lunchtime I'll put them in the henhouse with some blue esky ice blocks to sit on and I'll get the misting going.)
But other than being confined to quarters or confining herself to quarters in the heat, she's been enjoying all day every day in the yard. Dust bathing, snoozing, foraging, etc. So she's got plenty to think about and plenty to do - they all have. So if she's plucking her own feathers, it's not from boredom.
I still haven't seen her plucking at her feathers, but I'll keep watching.