Doing dishes

I'm really trying not to take over all of Mom's chores, but it's getting more and more difficult.
I do all the cooking and Mom wants to do the dishes, mainly because she thinks I don't get them clean enough.
We are almost out of dish soap, but we have just enough for tonight's dishes. Instead of using the last dab of soap, I caught her getting ready to squeeze some Jet Dry in the dish water. I just lost my temper at her because she scared me. I asked if she wanted to make us sick and I actually yelled at her. I squeezed the dish soap into the sink to make enough soapy suds and left her. I tossed the Jet Dry and the empty bottles of soap into the trash and will clean out the rest of the cabinet under the sink tomorrow.
I know I shouldn't analyze how her brain is working, or rather how her brain isn't working, and I really have tried to just accept how she acts and thinks. But it's things like this that just plain scare me. And because it's the second time I've caught her doing this, I wonder how many other times she has done it. The first time I caught her putting Windex into the sink to wash dishes with, but that was a few months ago. That scared the living daylights out of me. And that was after I caught her trying to use Windex to dust the furniture.
There are little signs she may be declining, such as not being able to read the numbers on a clock to tell the time and not being able to read what day it is. I know she thinks it's just easier to ask me, but when I ask her if she can't read the numbers on the microwave, she says she can't. And when I ask her to do it in front of me, she reads each number one by one, not like she's reading the time of day.
I guess it's just been a long day. I catch myself waking up in the middle of the night waiting to hear Mom breathe or make some kind of sound. I'm sleeping in a chair in our living room so I can be close to her and hear her if anything happens. I'm finding it more difficult to sleep each night.
So tonight when I say my prayers, I will ask for patience and understanding - again. And most of all, LOVE.