Cheryl,
We all have our own way of helping, your way is just as supportive as your sisters, it takes a combination of all to be there when a loved one is in a health situation. You were there for her, I am sure it was very important to your mom. Never doubt your capablility, holding her hand , being there is most supportive. I am sorry for your loss , the hole you feel will fill memories of her in time, but you will always be sad she is gone..much love to you, Ginger Beane