Helping as much as I can, but my sister wants more...

My mother has had cancer about ten years, and it has slowly progressed to the point that she is bedridden. My father took great care of Mom, but looking back the strain probably killed him. Mom and Dad were still living in the house they built over sixty years ago. After Dad passed, my sister, who never married and has a home-based business moved in with Mom, who was deteriorating rapidly. I had already taken over the care and maintenance of their two acre yard and home; Dad just wasn't able to juggle it all toward the end. My career takes me all over the world, and I juggle the care of Mom's home, my primary home, and a multi-acre property in the country.

Mother's health declined to the point her physician basically told her there was nothing else that could be done; she's 92, the cancer has metastasized, and chemo was not working. Well that was 19 months ago, and though she has had a dramatic weight loss, her mental prowess still amazes me (she works the NY Times crossword puzzle in about ten minutes).

Physically though, she's a wreck...multiple hip fractures, osteoporosis, and frequent UTI's. I'm a strong guy, but to pick her up and place her on her "port-a-potty" is all I can handle; I don't see how my sister can do it at all. We have hospice (she's bathed 3 X a week and a nurse visits 2 X), but my sister isn't coping well with the stress. I relieve her as much as possible, but she is shouldering far too much of the load and resents it when I tell her she can't continue to bear the brunt.

I am married, and my wife's mother is also infirm. How can I intervene when what my sister wants of me is more than I can give? I stay at Mom's about ten days out of 45 to give sis time to decompress, and stay about one full 24-36 hour period every week so she can get out with friends.

Whenever I ask her about using an overnight sitter, she gets mad at me as though I don't think she is doing a good job (even though I continually praise her). Mom notices the friction and would be very hurt if she knew the extent of sis's resentment. I just want relief for my sister; I know we can't be primary caregivers (Mom does not want to leave the house that Dad built - it feels like she thinks that would be an abandonment of him). We always got along really well, both of us love her dearly, loved Dad dearly. I am concerned about my sister's mental health.

HELP!