Is it even worth fighting back or explaining myself to a toxic mom who now probably has dementia?

Personally I would not bother to explain. By not responding you are pretty much telling her that what she said didn’t really matter to you. I would be ready if it or something similar comes up again. I really like the grey rock method and responding but saying nothing. So for example if my mother said something like that I might say.

Well that’s how the world is now. We are all so busy getting stuff done. You are so lucky you grew up in a simpler time.

Or some other such nonsense.

Decide what your goal is with Mom. If you want boundaries, including emotional ones then don’t engage when she throws a guilt trip at you. I know it’s not easy when they push your buttons but if you tell her off what will her next play be. My mothers would be the silent treatment, which is fine, but then you have to deal with that when you go see Dad.

Back in October, you posted about cutting off all contact with your mother. How did that go?

Is the plan to have a 24/7/365 caregiver until both of your parents are gone? If there is a 5-day caregiver, is there another one on the weekends?

Your mother has POA over your father, and you think your (uninvolved) sister has it over your mother? You also wrote that their house is awful...messy, dirty, cluttered, needs repairs, or what?

I wish you could find a way to just check on your dad periodically, and have your sister be the one to be concerned about your mother.

I’d suggest 3 strategies:

1) Make a plan to see your Dad on his own. Perhaps difficult, but it might be possible.

2) Wear earplugs with your mother. The doctor has recommended them because you have a recurring ear infection issue. Then just talk yourself, don’t even try to listen.

3) Skip short visits, and decide in advance the length of time you will give to mother. Plan what you are going to say, don't go for a two-way exchange.

If she is developing dementia trying to explain will not get you anywhere. You cannot explain to dementia.

Instead just let her comments to in one ear and out the other. Ignore it. Do what you want as far as visiting.

I would explain to her. (She won’t listen and she’ll argue). But for your sake, explain to her: get it off your chest.

However, you don’t need to be an open book and explain everything: she’ll use that knowledge against you.

I myself use strategies against my abusive mom - but if I explained to her how I do it, she would use it against me.

So I’d say: OP, explain to your mother what you feel like explaining. Get it off your chest. For your sake.

“I have a sister, btw, who never sees her but somehow remains the golden child.”

So common. So unfair. 

“Mostly, I've been her favorite target for whatever is wrong with her brain.”

That’s what abusive people do: they blame everything on you. You’re innocent.

I wouldn't bother explaining anything to your mom. She's a real piece of work. And you don't need to get into an argument with her. Just let it go. If you want to check in on your dad, cool. Do that. I see nothing wrong with having very short visits. Do you get to spend any time alone with your dad? Or are they always together?

Look into grey rocking where you don't engage. Don't let her get under your skin. SHe's not worth it.

Nope, not worth it, you’ve tried.

My first reaction is protection.
Keep yourself safe for the time you are exposed.

We are not made of steel, so yes, keep on with building your boundaries. They may include less visits, shorter visits, phone visits instead? Or always taking someone with you. (Hey I just wrote out MY tactics 😁)

I don't have toxic to deal with, but do seem to have cracks/ holes in my walls that stuff seeps through. (Just made or trained that way). I come home with what I call an 'emotional hangover'. Have taken on others feelings & must go for a run or a hot bath to shed them.

Your Dad has progressive health problems & must have high needs. Your Mom kind of does an 'emotional dump' on you as you appear in sight, right? People with unmet needs can do that. To be 'saved'. To gain attention? Or because she is depressed? I don't know.

Mom may well need much support. Maybe think of her 'woe is me' line as a rope. You don't have to catch it. It could in fact be dangerous to do so - pulling you under.

Instead, advise her where to seek help for herself.

Mom, sounds like things are quite tough for you. Have you talked to (insert: Doctor, Geriatrician, an Aged Care advise service, a therapist, a helpline) ?

Everytime Mom throws that rope at you, aiming around your neck DODGE it.

You can point her & her rope of woe to a professional for help instead.

My mother was similar, in that our visits with her were never 'enough' and she would beg everyone to stay longer when we came. It created a situation whereby nobody wanted to go visit her, in reality, b/c she played the guilt card SO hard, it was awful. From her perspective, she felt lonely and wanted our company for '17 hours' so yes, we understood where she was coming from. From our perspective, however, all she ever did was complain constantly, and snipe at others (the other family members who never did enough for her, the other residents in her ALF or her Memory Care ALF, the staff, etc). She would complain about everything from the food that was served to her to the size of the portions (not enough to fill a cavity) to the housekeeping to the quality of the laundry being done for her. She'd complain to the point where nobody could get a word in edgewise, and then when she wasn't complaining, she'd be carrying on about wanting to die. So each visit was dreadful, to say the least. Had I mentioned 'boundaries' to her, she'd have looked at me like I had 3 heads; no such word existed in her vocabulary b/c children had 'no right' to set down such boundaries with their mothers.

When she'd complain about my brief visits (which were an hour or more while she was in Memory Care AL), I'd explain to her that I had a meeting to go to or dinner to cook or whatever. Trying to explain anything logically to an elder with dementia doesn't work anyway, never mind trying to get through to someone with THIS type of mentality even w/o dementia does not work. You give an inch and they take a mile. The message is always clear: you should be doing MORE. Why aren't you? Which eventually left ME with the attitude of 'why bother doing anything if nothing is every good enough anyway?' That is the unfortunate result of the attitude these women portray to us. And the consequences they bring about as a result.

Explain yourself to your mother or don't; either way, it won't matter in the long run (in my opinion). They have already formulated their own opinions anyway, so what they hear when we speak is BLAH BLAH BLAH BLAH, you know?

Wishing you the best of luck maintaining your boundaries and your composure with a difficult situation.

Did your Mom ever fully understand you, or did she just twist your words and actions all her life??? If my guess is right, then nothing's new. If I am wrong then your poor Mom has lost her mind, and you must forgive her.
And to be frank I couldn't agree more with her. Why are you stopping by briefly? Why can you not allow yourself a day off from her? Are your visits making her happier? I doubt it. Are they making you happier? Your husband? I doubt it.
I myself would just say, "Sorry to have made your day only a bit worse Mom. We need to leave now and I will see you soon. And Mom, in future, if my visits make you happy I may stay longer, but if they make you unhappy I will leave at once. Love you. Kiss kiss; bye bye."
Your Mom could do with a little training. I doubt it will work, but I doubt anything else will, either. So, for me it would be when she is negative it is a short visit. When she is positive it is a longer visit.
As to this thing of the loved sister being perfect? Often parents like your Mom play the game of the other child being the good one and you the bad one, and somehow manage to play it with both children.
It is a bit late to figure out your relationship with Mom and to hope for change. She is now losing what mind she had. Who can know? Perhaps she will change to sweet, but given the fact that dementia pulls the stops on inhibitions that keep us socially appropriate, I wouldn't hope for that.
I am so sorry, but move on with your life. Decrease your time with Mom. Like most "abused children" you are still hoping for that one day when she says "You are such a good daughter. You are a fine person and I am so proud of you. I love you." It's not likely to happen until you choose a new family of friends who value and love you, and spend your time and efforts on them.
It breaks my heart to see kids who are long long grown up still so desperate for the love that was withheld. My heart goes out to you and I wish nothing but the best for you. As to mom, were I a believer I would be put in mind of as she sows so shall she reap. Sadly that doesn't always happen.