In what way does your apartment in the town where she lives, give her a hold over you? Does she look after it for you? If she does, that's nice of her, perhaps think about that when you're phoning ...
But if not - what hold? And exactly how would her being offended make visiting your apartment difficult? Wouldn't it just mean you wouldn't have to see her?
But, you asked for coping strategies.
Limit calls to as little as possible - once a month? Less?
Have the phone on speaker phone and be doing something else while you call - the ironing, or cooking.
Set a (short) time limit. When its up, interrupt mid-sentence with "ooh there's the doorbell/smoke alarm/baby/mobile", say goodbye without drawing breath and put the phone down.
If it makes you feel better, start every phone call with "I just thought I'd ring you as you haven't called me". Although tbh, if she's that bad, perhaps you should focus on being grateful that she never calls you.
Think of two things you'd like to tell her, and make sure you get them in. If necessary interrupt her mid-sentence and launch in, all loud and excited. When she ignores what you've said and talks about herself again, say "oh yes, lets talk about YOU!" in a bright excited voice. She won't notice but you'll feel better.
Don't respond - just "mmm" a lot and let her talk.