God and Karma

I have always believed in God, and also in Karma. But now my beliefs are severely challenged. I sincerely doubt everything I have believed in up till now. My mother had a stroke almost three years ago, with all the attendant horrors that go with it—-being paralyzed, unable to speak properly and so on. She has had to give up her home in order to go into care, and her dignity and privacy, and has faced it all with a brave and courageous spirit. But now, after all this hell, her eyes are going and she suddenly can’t keep her eyelids open. We have given her Botox injections, and these worked for a few months, but now they are not. As she also has macular degeneration, this means she may be unable to see as well as all the other disabilities she has. It’s too much. If there was a God, why would he inflict this sheer torture on my mother, who simply doesn’t deserve it? To make it worse, her mind is clear and she knows completely what is happening. I feel tortured watching her suffer. Is there any way you can help me understand why this is happening—–I would very much appreciate your help.