Anyone out there find that the parent they're caring for saves the crazy demented episodes only for them?

Mom has advanced PD and is becoming more and more 'confused' or mixed up -- the nice words for impending dementia. Problem is I'm the only one who gets a ring side view of this. I here 98% of the time so I see all the crazy crap. She's sweet as pie for her phys therapist who comes 2X a wk for an hour and for the home care person who comes only 2X a wk for 4 hrs. She never unravels for them and is sweet as pie. I'm noticing more and more that mom's episodes of confusion are becoming to the point where I can't say anything without being accused of being mean and horrible when all I'm doing is trying to explain myself. Can these seniors turn it on and off like a faucet or am I being paranoid?