What should we do when my sister says "stop helping dad"?

I agree that you should just not speak to her about your father and keep your conversations on other topics. If she has resentment or hard feelings towards your father, she may see your commitment to him as you taking sides (his side). I think that often, when one person has an issue with a mutal family member or friend, they want to solicit you to join their side (even if not directly stated). They want you to validate their feelings and agree with them. Even if you see that your sister has a valid point, and cause to be upset, you may just want to keep a peaceful, drama free relationship with your father and stay out of her issues with him. I hope she finds a way to see that.
I'm in a similar situation with my sister who hates our mother. I am my mother's primary care giver. I never tell my sister everything that is involved in her care. I just do what I have to. I agree that our mother is very difficult and demanding. We had a lot of drama in our lives growing up. It was a difficult childhood. I just want to do what needs to be done and keep the peace. There is always drama between the two of them and I get sucked into it. It's awful. No matter how much I try to mediate the situation or divert the argument, my sister takes issue with me. She wants me to join her against our mother and isolate her by cutting her out of our lives. I called on her once for support because my mother, like most chronically ill people with mental health issues, was driving me crazy. I started having panic attacks and an emotional breakdown. I had a horrible emotional outburst against my mother and said awful things. I could feel myself losing control and while I felt badly that I was treating my mother that way, I couldn't stop myself. I had hoped my sister would have come over and tried to mediate the situation; reason with my mother, who becomes very unreasonable, and help out; but, she didn't. She started yelling at my mother, calling her names, and started a war. She made it look like she was defending me but in reality, she had found an outlet for her hatred and tried to enlist me in her war. I didn't need that; I needed to make amends for what I said to my mother, and needed her to understand that she is wearing me down with her demands. I needed someone to work out a care plan where I wouldn't be driven to despair. Our mother continues to need care. She has no one. As challenging as she is, my sister knows that cutting her loose is not an option. If I did cut her loose, my sister would be too embarrassed in front of the extended family, and fear that she would be looked down upon, so she would tell me to help my mother or try to do what she could, but realistically, given her lifestyle, it would be minimal. It's easy for someone who is removed from a situation to talk and criticize because they don't have to deal with the practical realities of the situation. It's easy to say "out of sight, out of mind"; but when it comes to a parent-child relationship, you tread on a mine field of guilt, emotions, resentment and love. There is hardly ever a clean break.

The sister who really has had very little contact with dad does NOT get to make any decisions about his care. Period.

I have the same problem.My answer is to allow my sister be herself. i used to compliant about her helping me with the Care-Giving duties with my mother. I had to place my mother in a Assiting living to get some help. my mother love that place; she is not living alone and she have met some new friends.The resident form a strong bond and look out for one another.As you see I don,t worry about what my sister is doing anymore.I Just keep it moving and do what I can; to make my mother last days her best days and worry-free. Blessing to you.AMEN

"Seriously out of whack" of course it is. Let's get this straight - you are neglecting sis who is healthy, to take care of your 81 year old father with health problems? Sounds like sis wants everything to be about her. As our parents age; most adults realize that their parents need more help; those that are more concerned about themselves do not.

Since your already know that sis wont' help, sounds like you are the adult in the family. Why don't you try this: "dad need's more help now, but he is not ready for assisted living; what can you help out with? She probably will balk at that, but it may stop the complaining.

Sorry you have to go through this. It is not uncommon for one family member to do all the work and for others to be critical of what they do.

I always seems that the child least involved has all the answers. Sort of like a person who has never had kids telling you how to raise yours.

You aren't going to change her. I would never mention your dad to her, call her a little more often or send emails or texts. Emails and texts are great, sort of a one way conversation. When she brings it up, You can always say, "You could be right, I'll have to think about it" and drop it.

Because of family dynamics, I never mention one of my daughters to the other one. I do this with both daughters. Because what I have learned, they immediately call the other one and put what I have said in the worst light. So, when I talk to one, it is like the other one doesn't exist. I would try this with your sister. If she asks about dad, just say he is OK or something like that. That is unless he has a real problem.

Just a thought, could she be right?

No, not really familiar. It's been clear for years she wasn't that interested, and I've been fairly successful in focusing on other topics. She's usually the one to bring it up.

I do agree she's conflicted and looking to not have to change. I guess in the end, it doesn't matter whether that's realistic on her part or not.

Does this scenario sound familiar? Sis calls for your customary chats and inevitably  you share some concerns about dad (or mom when she was still alive). You maybe mention about how you have to go there so often to keep an eye on things, sometimes you may even whine a little about how hard it is to schedule your life around his needs and how nice it would be if sis was closer so she could share the load. Even when your mom was still alive the conversation started to change, instead of the nice light one on one sister time you used to share the conversation became focused on your parents and their needs. Sis just wants the return of the relationship you used to share before your priorities changed, she's too far away to help (and she may feel guilty about that), and she's too far removed to emotionally be as invested in him as you are. At this point I think you have to decide whether it is worth it to you to maintain the relationship on her terms, because I doubt anything will change on her end.

Yes, we've always been close, although she became more critical of me even before our mom died, and it's less fun for me to chat with her in general.

Can you tell us a little bit more regarding the history of your relationship with your sister? Have you always been close?