sister and telephone calls

Hi this is my fist time posting here. I will try to be brief. My sister and I have always been close. She is a lot quieter than I am and 4 years younger. She has always as long as we can remember suffered with bouts of depression she is under the care of physician and takes medication. She no longer speaks to both my other siblings or my father. In the past year her husband has been diagnosed with a chronic illness. He is now home from work everyday. She works approx. 20 hrs a week. Almost everytime I call it's the wrong time. I should mention for financial reasons I have always done the bulk of the calling. At least every other day. I hear the annoyance in her husbands voice. "Yeh" I'll get her now" sometimes they just refuse to answer. Often times there are others in the room with her. Her neighbor is going thru a divorce and she needs constant attention. I offered to pay for my sister to visit many times in the past 8 years since I have moved here but I always have to go there. If this where a friendship it would be over no one would take this. My younger sibling said you need a medal how to you put up with that behavior. I have asked "when is a good time to call? anytime was the reply. If I tell her how I feel I'll end up in the same position as my brothers on the do not call list. Any ideas. I really do love her and miss my sister.