Tedber, I was thinking exactly the same about the friend being worried about her memory. That makes my Mum furious when I say, "I did tell you," and she can't remember. I'm beginning to realise that a quick, "Oh dear, I thought I had," makes life a lot less stressful for both of us!
ninathenana, is it possible that you hadn't told your friend but thought you had? Presumably you can check the message you sent her originally. If you have 'evidence' you did, then it would certainly make it more possible that her memory is failing. It might make you feel less angry if you can get a handle on why she is acting this way.
Ultimately, I guess if it comes down to her needing to be the centre of health attention, it depends whether you are happy to continue a friendship which is a bit one-sided. I guess if you have managed for 30 years, you must get something out of the friendship. All relationships are a balance of the good and bad. All the time the balance is more towards the good, it is probably
worth persevering.