Some really good suggestions on here. Maybe suggest that - to get her mind off her troubles - she come over to your house to help you with your housework, gardening or whatever, as you feel swamped and stressed every day
Seriously though, I have had some really difficult things to cope with over the years and I do tend to distance people who sap my mental energy with what I consider minor troubles. I suggest that when she does ring, you MAKE the conversation about you. Talk about yourself and what's going on in your life (without pausing if possible) - maybe even put some notes of what you can say to her next to the phone, in preparation for the next call. Some people don't know what it's like to be "talked AT" rather than talked to, until they experience it themselves. It also might help your friend to be forced to hear your troubles, as people who are self-absorbed don't always know how to put themselves into the shoes of another. One thing in her defence: people don't tend to grow stronger and more compassionate until they themselves are placed in situations where they need to learn. So, on a scale of 1 to 10 (10 being so bad you can't cope), you might be feeling a 9, but she, likewise, might be feeling a 9. The fact that, to an outsider, her experiences are far more minor than yours, doesn't change this. Nevertheless, she DOES need to learn how to be considerate to you, and your response to her calls will teach her this.