Does anyone have extreme resentment towards a sister for absolutely doing NOTHING to help?

You need to find a way to let the resentment go. I am saying this as an only child who has no one else to look to for assistance. You can't decide what others should do, you can only decide for yourself. You decided to take on more than you can handle, that is not on your sister. Not everyone can be a caregiver. It would be nice if everyone could pitch in but that just doesn't happen in real life.

Another poster mentioned that the 'great' mom you had may not be the same mom your sister had. My dad is the 'fun uncle' but he wasn't a 'great dad'. And my cousins will never be able to see that.

You also give your brother a pass but not your sister....and you don't mention the other sibling at all. You have to decide what you can do, and that is it. You can't make others pick up the slack. If you mom needs more help, then help her arrange for outside help. It all doesn't have to fall on you. I have a friend who's elderly father got used to her brother stopping by every day after work. That is a lot. Friend would take him to occasional doctor appointments but could not commit to being there every Friday. It got to be too much for her brother to stop by every day and he expected her to pick up the slack now that it was too much for him. He set the precedent and when he couldn't keep up was mad others could not just jump in. Same thing here. You decided to take on all this extra work, not your sister. You can't dictate what she does, only what you can do. If you aren't healthy you won't be able to help her at all.

I used to have huge resentment towards my brother for doing absolutely nothing, but I think I'm mostly over it now. He did nothing when our father went into decline, did nothing when our stepmother got terminal cancer, and does nothing now for our mother. We got in a huge fight about 3 years ago and stopped talking for awhile - basically the fight was because he lived in the same town as mom and did nothing, while I was driving 4 hours once a month to help out with things she was no longer able to do, like yard work or deep cleaning. 2 years ago I pushed her to move to my town. Just this summer my brother and I started talking again, when he finally came to visit mom after the move - for one night.  I decided to act like the fight never happened and fake my way through being welcoming for the sake of my mother's mental health.  (She has end stage renal disease - it would be optimistic to say she will live longer than 2-3 more years.) 

I find my brother has grown into a negative, self-centred, and judgemental person, and the truth is, I've realized it's easier to figure this out on my own, than to bring that energy into our lives. I know I'll need a break soon, but I'm going to do it with paid respite. I strongly urge you to do the same. I have never experienced caregiver burnout, but I have experienced non-profit job burnout, and it literally almost killed me in the end. Please don't let yourself get so sick that your "break" ends up being 2 weeks in the hospital trying not to die, like mine did.

yep. I feel your pain. I took care of my FIL, my husband was the youngest of 14 and not one of the others bothered to help at all. Until the last week of his life when the doctor said he would not make it to the weekend, then my house was packed with 10 other siblings, all looking to get a piece of some non existent inheritance. Thank goodness for hospice and social services. My husband also hired a caregiver. Do not wait for your sister to come around and help you. Look out for yourself.

One thing you can do to help let go of the resentment & anger that is burdening you is talk it over with a therapist.

I would advice your sister to seek counseling also, to help her overcome her disgust and at least visit Mother. But she didn't ask me.

Your sister may not see mother fantastic and wonderful. Each child has a different relationship with each parent. That is one possibility.

You know that your brother "is a wreck." You don't expect him to do more than his illnesses allow him to do. You are caring for him. Try to see your sister's lack of caregiving instincts and failure to be nurturing toward your mother as a defect, a flaw she didn't choose any more than your brother chose to be bipolar.

Perhaps it would be less hard on you to direct your resentment and anger at your mother's failing health, your brother's illness, and your sister's limitations, rather than at the people who have these impairments.

When it comes to getting help, you absolutely need it and deserve it! In this regard, consider yourself an only child. Effectively you are the only one who has/can step up and take over. But you need help! You need respite care! As an only child how can you get that help? How do other only children do it?

Your question, and this thread, is about resentment. If you want help figuring out how to get particular kinds of help, post again with that as your question. You'll get all kinds of advice from the AgingCare family.

Stop waiting for your sister to have a personality transplant. Look for respite care elsewhere, and TAKE THAT BREAK!!!

It's well within the rules, by the way, for that care to be billed to your mother. But you do need some down-time, not least because if you crash your sister will no doubt have the pair of them in institutional care before she can say "what's a Depend?"