Feeling terrible about living long distance.

I live 6 1/2 hours from my mother, but I have 2 sisters who live in town and also a brother who lives 3 hours from her. I am the youngest and they are older than me by more than 12 years. After a lot of bad financial dealings by my brother, who was DPOA, my mom added me to the DPOA to ensure her business was taken care of and then I became the payee representative for her account when money became missing. I had been doing all the visiting (rather than my brother) and checking on her doctor appointments, etc. My husband and I lived closer until 2007 when his job relocated us. When we lived closer, we always visited regularly and took her out to eat, mowed lawn, bought things to help her for her home, etc. The sisters who live there didn't spend quality time with her. One never went to her home to visit, but my mom would go visit her. The other sister sister would visit about once a week and would take her candy, or a few items here and there, but never took her out or invited her to spend the night at her house.
My mom's dementia caused us to move her into my sister's home over a year ago, (the sister who never visited her at home). Over the last year, I went home about every two weeks, made doctor appointments that my husband and I would take her to, cateract surgery on each eye, and 2 followup visits for that every 2 weeks. The sister my mom didn't live with never offered to help take her to appointments, never offered to help the other sister out by taking my mom for even one night. She was also too busy cleaning her house, or complaining that she couldn't bath her because she had had knee replacement a few years ago. When I lived closer I would try to arrange "girls day" with my sisters and my mom to go out to lunch or breakfast and take her shopping. Only once did one of my sisters go (not the one my mom lived with). They always had things to do and couldn't go.
Long story short, back in May I went and got my mom to stay with us for 2 weeks to help my sister get a break and also spend some quality time with my mom. After a week she fell getting up out of bed, broker her hip, had surgery here and her dementia worsened. She was here about 2 1/2 weeks after surgery and the rest of the family was on me about getting her transferred back home so they could visit her. My husband and I were with my mom 24 hrs a day, taking turns spending the night with her at the hospital. We didn't want her to feel alone. My brother had been 1 hour away visiting a cabin when my mom was having surgery. He showed up the day after surgery to tell me he blamed me for her getting hurt because I should have never brought her so far away, AND he wanted her taken back home. My sisters did come up to visit her, but the sister who never helped out much complained the entire time and also made it clear that if my mom went back to her town, she would not be able to visit all the time. So, I got my mom transferred by ambulance to the local hospital where she lives. My husband and I followed the ambulance for the almost 7 hour drive, got there at 2 a.m., made sure she was comfortable in her room before getting a couple hours sleep at a hotel (we have to stay at a hotel since there's no one to offer their home). I went to the hospital by 8 the next morning and stayed all day before going back home. I drove back to see her less than a week later when she was getting moved to a rehab nursing facility. I sat at the medicaid office for over 3 hours doing paperwork for her long term medicaid, again, no one offered to go with me or help with anything.
Now, my mom has been moved to the long term section and the sister who complains about helping is at it again. Her husband and her visit my mom around lunchtime to help her eat, but she is so angry and feels like she is obligated to go. She is making the nursing home staff think she and her husband are the only ones doing anything and causing attitudes . She has also told me and my husband we should move back there because "that's where I grew up"....translation..."you need to move back so I don't have to go visit mom all the time".
We are still going home every 2-3 weeks to visit I usually get there later afternoon and go straight to the nursing home for a couple hours, then all day the next day and a couple hours the morning before we leave. I have other obligations at my home as well, which my sister is aware of and has no empathy for what others are going through, only herself.