@EmJay1 this is a difficult situation for you.
I wonder if it is worth you writing to/emailing your sister setting out exactly what your mums care requires and how much of it falls on you. Then ask her the question, “if I fall ill, and cannot do this for a period of maybe several weeks, what then?” Is she going to step in and take over? Or take responsibility for arranging emergency care and support?
You may have tried this already, or have reasons why it isn’t appropriate, but it might be worth a try. In the current situation any of us could fall ill and be required to isolate for at least two weeks, so it seems a very relevant question.
I wonder if it is worth you writing to/emailing your sister setting out exactly what your mums care requires and how much of it falls on you. Then ask her the question, “if I fall ill, and cannot do this for a period of maybe several weeks, what then?” Is she going to step in and take over? Or take responsibility for arranging emergency care and support?
You may have tried this already, or have reasons why it isn’t appropriate, but it might be worth a try. In the current situation any of us could fall ill and be required to isolate for at least two weeks, so it seems a very relevant question.