How do I deal with my mom when she suddenly gets mad at me, on the phone, and tells me she won't call me again?

This is just one of many incidents. Long story short, As I was driving home, I was listening to her rant and rave and complain about her cleaning lady not staying long enough today, etc., and I offered advice, here and there. She kept fussing about this over and over.. I finally said that I had to go because I was nearly home and it was storming, and I needed to get out of the car, quickly. She took this to mean that I was bored with everything she said (I was listening, quietly, to her), that I didn't want to listen to her or talk, and she hung up. I knew she was mad, but I called her back when I got settled in the house. She finally answered and said that she wouldn't be calling me anymore, since I didn't want to listen to her, that I could call her if I wanted to. I just said ok, whatever you want. I didn't argue. And she hung up the phone. How do I deal/look at this situation? She is 80 and stays in the bed most of the time, due to some physical problems. She is also very depressed. Any advice would be appreciated! (BTW, I am an only child, have a full-time job, and am raising triplets (with my husband.)