A few years ago, me and my mom moved back in with my grandmother. Her dementia just got worse and worse as time progressed. My mom is trying to help her, but my grandmother is not only forgetful, sometimes she seems almost spiteful and vindictive and it is confusing and painful. She will leave the doors to the outside open and then when we gently ask her to close them (the level of pollen, dust and ozone in the environment makes both my mom and me nauseated, anxious, gives us stomach cramps) my grandmother will get angry and even threatening when we try to close the door before my mom ends up stuck back in bed with major stomach pains or I end up hyperventilating in a corner, crying my guts out, rocking. Whenever we try even the lightest encouragement to make the environment more tolerable (keeping windows closed, keeping my grandmother's door closed when she is opening her own door all the time to go out to the back yard, asking her not to sit down on my bed when she is in our room and covered in ozone, pollen and dust or picking up my pillow, my stuffed animal) she becomes sharp, disgusted and tells me to leave her alone, or get some guts, or the only reason why I get sick is because my mom talks about being sick 'all' the time - basically I am gullible and suggestible. I try to keep in mind that dementia - even her light case - is like what children act like and she really can't help it, but she is doing it more and more and every time it happens it feels like every nerve in my body is on fire. I have so much trouble sleeping because it is miserably hot where we live and I have to sleep out in the living room during the summer if I want to get to sleep before 1am. Then - more often than not - I am woken up at around six am by her slamming the fridge door and cupboards, or turning off the fan above me so I am panting like a dog from the heat. It's constantly new things. I often sit up for an hour or two then and just cry, or hyperventilate and hate my life and my grandmother. I need about ten to twelve hours of sleep to function but I don't remember the last time I got even near that much. I remember how I used to love her and now she just seems so nasty and hurtful. Sometimes she tells me and my mom to get out of her house, that we should be grateful we're allowed to live here. But she doesn't seem grateful that my mom is taking care of her even when my mom is exhausted and just trying to get better, and she doesn't understand that she makes me feel scared. My mom has taken all this time to help her when she could have just been taking care of herself and if we have to move out it would be very bad for us both. I know this won't likely happen but there is some part of my mind that just feels under siege and stuck in a poisonous situation. I'm sorry if I sound like I'm whining but I just feel like I needed to get this out. I can't really do anything about it right now but this.
My first suggestion to you: Put a small air conditioner in your room. Keep your grandmother and your mother out (gently-or with a lock on your door). Sleep only in your own space. There is no reason (if you have your own room) anyone needs to come into your safe, clean space and sit on your bed. Try that.
Do you have any other options for living someone else? I consider my options if you and your mother intend to keep her in the house.
I will add that over time, the odd and unpleasant behavior of my cousin subsided and she is quite pleasant now. She's content and not mean or hateful at all. I'm not sure if it was the progress of her dementia that caused it or the fact that she was treated for anxiety and depression with medication. Regardless, she's much better now.
Best wishes to you and your family.