How do you tell a person with dementia they smell without them getting cranky?

Please read something about dementia. You seem to not know anything about it.

The brain of your person is dying. Your person can no longer understand instructions or discussions or when you tell them they stink. They have lost that capacity and they will never get it back and it’s only going to get worse until they die.

He/she has likely also lost olfactory senses so he/she doesn’t understand or know that she stinks. If she knows she stinks, she has no clue that she needs to do anything about it or what to do about it; she can’t care. This is dementia.

Its not that she won’t was properly, its that she has lost the ability to wash properly. She doesn’t know this is a problem and if she has an inkling that it’s a problem, she can’t care. This is dementia.

She likely has no idea what a pad is, why you want her to use it or what to do with one anyway. She likely doesn’t recognize the pad and she can’t care that you want her to use one. This is dementia.

She likely has no idea what you mean when you say she stinks. This is dementia.

It’s only going to get worse.

You don't tell them.....you bring them into the bathroom and help them shower and change their soiled briefs. She smells because she has dementia and has gone nose-blind to odors, and requires help with all activities of Daily life now. If you're unable or unwilling to give her that help, then hire an aide or get her placed in Memory Care Assisted Living or Skilled Nursing.

You don't tell them, you help them deal with the problem with compassion.