Even tho you love her, she is a toxic person. If you have to for your own well being spend less time talking with her or find a way to emotionally distance yourself.
I'd be upfront and tell her that she's Debbie Downer which makes it difficult to spend time with her on the phone. Remind her you live too far away to visit. I would make the suggestions you have if she's willing to listen. If not, tho it'll be difficult, separate yourself from her neediness. If that means making less calls, so be it.
And/or you could try to make an emotional separation from her and then just listen without getting emotionally involved. You are not responsible for her happiness.
No matter what you do she's going to feel that you don't love her. Isn't she already implying that with her pleas. Your first responsibility is to take care of yourself and your family.
My mother wanted more of my time than I had to give. I always felt guilty and pressured. I was in counseling for depression. I learned that my happiness was as important as my mother's happiness and that I could just say no to her requests. I felt liberated but still very sad. I found it easier to deal with my feelings than with hers.