Being the eldest, yorkshire and probably a bit of a control freak, I tend to dot the i's and cross the t's before any event. So for example I offered to take 3 women who no longer drive to Saltburn, but setting out my offer, which was that we should share the cost of fuel, but once there do our own thing and meet up at a convenient time to return. One person started to say Oh we could do such and such, which I immediately jumped on and said No that was not what I am offering. I am suggesting you have a day of freedom to do your own thing. She was a bit huffy but it has been a great success and have done it a couple of times, and we all understand the way it goes and they actually like having their own space now. So there are a couple of things in your situation that you might suggest.
1. use the new year as an easy way to present it as a new years resolution, where you can have a coffee with her and tell her now with the cost of living and being retired etc etc you need to curb your spending and so perhaps you may not manage to meet up so much, and that if you do it would need to be for a coffee rather than lunch sort of thing. Then go on to the cost of fuel and that you cant afford taxis etc and be ready to suggest a cafe that is on a bus route for you, where you could say that you will be fine with that as you have your bus pass etc. If she is any sort of friend at the least she will be apologetic for being so thoughtless , and she should be thanking you for all you have done so far and arrange to pick you up instead!!
2. The next time you meet again stick to a cafe on a bus route sort of thing, tell her you are thinking of not going to something you normally do so play bridge or golf or whatever, because it is now becoming too expensive for you to continue, and that can easily lead onto talking about other friends with similar ideas and how you all now meet up in the park for a walk or go swimming and have coffee together afterwards, as it is too expensive to carry on as you used to.
3; You might suggest if the distances are not too far that you could instead go to each others houses for lunch. That way you have more time to chat and catch up and again dont try at all to compete with each other about the food, but go for something simple like a jacket potato with some casserole that would be easy to prepare in advance and would be no problem if you were delayed.
I think all of these suggestions still show that you value the friendship enough to keep in touch , but on your terms. If she is a friend , she should be mortified that she has not realized what she is doing and has been very selfish and thoughtless to say the least. Doesnt say much for the other women in the group that have also been thoughtless to say the least. I think she should be making it up to you and that in the new year you can have a meeting on a more even keel.
If on the other hand she drops you, tries to excuse her behaviour, or backs away from the lunch idea without offering something else that shows more care then you will have your answer and she will be no great loss to you. At least that will have shown you a slightly different way to look at the way you are treated , and perhaps my upfront way of things is not very "british" the usual dont talk about money etc., but I have found that being straightforward and putting your cards on the table has been very beneficial. Friends have told me that when they are used to the idea it has been worth doing in other circumstances. You know those times when someone suggests something that you dont particularly want to do , but you agree , thinking they really want to and later you find that neither of you really enjoyed it but did it to suit the other person. At our age life is too short to waste it doing things that you dont want to do and being where you dont want to be. The pleasures of friendship are enjoying each others company and knowing someone for so long that you can tell them what matters, and be sure of an honest answer.
If you feel this is too direct you could simply tell her next time you meet up of a friend of yours who you think is being taken advantage of and ask her if you think you should tell your friend or keep quiet, but that you dont like to butt in, but that it is not a fair situation. However she does seem the sort of person who does not take hints even when given in heavy boots,!! We are all here for you and so you do not have to take any of our advice but it does quite help to read other peoples ideas and then that can percolate through your mind and you will actually come to the conclusion, possibly without even seeing her as to whether it is worth keeping in touch. Sometimes changes in situations can mean that friendships simply peter out, whatever happens between you two, you will have something to look back on , if you find yourself becoming in a similar situation, and be ready to stamp on any advantage taking. I wish you a clear decision, and that you will feel calm and satisfied by what ever you decide to do.
The other very very simple way I have used is to just think if she asked you to meet up on a particular day, and another friend did the same, which one would you choose to go to meet? You may actually already know what way you want to go and writing it down to us helps clarify it for you.
Whatever you decide will be right for you and then write it down somewhere and put that away, so that if you start to doubt yourself go back and look at your decision and the reasons for it to remind you of your reasoning and choice.